diff --git a/python/core/auto_generated/processing/models/qgsprocessingmodelchildalgorithm.sip.in b/python/core/auto_generated/processing/models/qgsprocessingmodelchildalgorithm.sip.in
index 645b9fe7dda..574dbed4d13 100644
--- a/python/core/auto_generated/processing/models/qgsprocessingmodelchildalgorithm.sip.in
+++ b/python/core/auto_generated/processing/models/qgsprocessingmodelchildalgorithm.sip.in
@@ -275,6 +275,9 @@ The ``currentIndent`` and ``indentSize`` are used to set the base line indent an
 The ``friendlyChildNames`` argument gives a map of child id to a friendly algorithm name, to be used in the code to identify that algorithm instead of the raw child id.
 %End
 
+    virtual QgsProcessingModelComment *comment();
+    virtual void setComment( const QgsProcessingModelComment &comment );
+
 };
 
 
diff --git a/python/core/auto_generated/processing/models/qgsprocessingmodelcomment.sip.in b/python/core/auto_generated/processing/models/qgsprocessingmodelcomment.sip.in
new file mode 100644
index 00000000000..b1c00441f5b
--- /dev/null
+++ b/python/core/auto_generated/processing/models/qgsprocessingmodelcomment.sip.in
@@ -0,0 +1,56 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/processing/models/qgsprocessingmodelcomment.h               *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+class QgsProcessingModelComment : QgsProcessingModelComponent
+{
+%Docstring
+Represents a comment in a model.
+
+.. versionadded:: 3.14
+%End
+
+%TypeHeaderCode
+#include "qgsprocessingmodelcomment.h"
+%End
+  public:
+
+    QgsProcessingModelComment( const QString &description = QString() );
+%Docstring
+Constructor for QgsProcessingModelComment with the specified ``description``.
+%End
+
+    virtual QgsProcessingModelComment *clone() const /Factory/;
+
+
+    QVariant toVariant() const;
+%Docstring
+Saves this comment to a QVariant.
+
+.. seealso:: :py:func:`loadVariant`
+%End
+
+    bool loadVariant( const QVariantMap &map );
+%Docstring
+Loads this comment from a QVariantMap.
+
+.. seealso:: :py:func:`toVariant`
+%End
+};
+
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/processing/models/qgsprocessingmodelcomment.h               *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
diff --git a/python/core/auto_generated/processing/models/qgsprocessingmodelcomponent.sip.in b/python/core/auto_generated/processing/models/qgsprocessingmodelcomponent.sip.in
index e1c3385662d..faa9e21577c 100644
--- a/python/core/auto_generated/processing/models/qgsprocessingmodelcomponent.sip.in
+++ b/python/core/auto_generated/processing/models/qgsprocessingmodelcomponent.sip.in
@@ -10,6 +10,7 @@
 
 
 
+
 class QgsProcessingModelComponent
 {
 %Docstring
@@ -86,6 +87,21 @@ in the graphical modeler.
 .. seealso:: :py:func:`linksCollapsed`
 %End
 
+
+    virtual QgsProcessingModelComment *comment();
+%Docstring
+Returns the comment attached to this component (may be ``None``)
+
+.. seealso:: :py:func:`setComment`
+%End
+
+    virtual void setComment( const QgsProcessingModelComment &comment );
+%Docstring
+Sets the ``comment`` attached to this component.
+
+.. seealso:: :py:func:`comment`
+%End
+
     virtual QgsProcessingModelComponent *clone() const = 0 /Factory/;
 %Docstring
 Clones the component.
diff --git a/python/core/auto_generated/processing/models/qgsprocessingmodeloutput.sip.in b/python/core/auto_generated/processing/models/qgsprocessingmodeloutput.sip.in
index 97c153991f9..dfa373e2591 100644
--- a/python/core/auto_generated/processing/models/qgsprocessingmodeloutput.sip.in
+++ b/python/core/auto_generated/processing/models/qgsprocessingmodeloutput.sip.in
@@ -127,6 +127,9 @@ Loads this output from a QVariantMap.
 .. seealso:: :py:func:`toVariant`
 %End
 
+    virtual QgsProcessingModelComment *comment();
+    virtual void setComment( const QgsProcessingModelComment &comment );
+
 };
 
 
diff --git a/python/core/auto_generated/processing/models/qgsprocessingmodelparameter.sip.in b/python/core/auto_generated/processing/models/qgsprocessingmodelparameter.sip.in
index 2c42438cb1c..cb30079323f 100644
--- a/python/core/auto_generated/processing/models/qgsprocessingmodelparameter.sip.in
+++ b/python/core/auto_generated/processing/models/qgsprocessingmodelparameter.sip.in
@@ -63,6 +63,9 @@ Loads this parameter from a QVariantMap.
 .. seealso:: :py:func:`toVariant`
 %End
 
+    virtual QgsProcessingModelComment *comment();
+    virtual void setComment( const QgsProcessingModelComment &comment );
+
 };
 
 
diff --git a/python/core/core_auto.sip b/python/core/core_auto.sip
index d9dd8e4b463..224ee3552a2 100644
--- a/python/core/core_auto.sip
+++ b/python/core/core_auto.sip
@@ -415,6 +415,7 @@
 %Include auto_generated/processing/models/qgsprocessingmodelalgorithm.sip
 %Include auto_generated/processing/models/qgsprocessingmodelchildalgorithm.sip
 %Include auto_generated/processing/models/qgsprocessingmodelchildparametersource.sip
+%Include auto_generated/processing/models/qgsprocessingmodelcomment.sip
 %Include auto_generated/processing/models/qgsprocessingmodelcomponent.sip
 %Include auto_generated/processing/models/qgsprocessingmodeloutput.sip
 %Include auto_generated/processing/models/qgsprocessingmodelparameter.sip
diff --git a/python/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in b/python/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in
index 2c2722f52c4..59ccab55a38 100644
--- a/python/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in
+++ b/python/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in
@@ -147,6 +147,13 @@ Returns the best link point to use for a link originating at a specified ``other
          - edge: item edge for calculated best link point
 %End
 
+    virtual void editComment();
+%Docstring
+Called when the comment attached to the item should be edited.
+
+The default implementation does nothing.
+%End
+
   signals:
 
 
@@ -208,6 +215,11 @@ Returns the stroke color for the item for the specified ``state``.
     virtual QColor textColor( State state ) const = 0;
 %Docstring
 Returns the label text color for the item for the specified ``state``.
+%End
+
+    virtual Qt::PenStyle strokeStyle( State state ) const;
+%Docstring
+Returns the stroke style to use while rendering the outline of the item.
 %End
 
     virtual QPicture iconPicture() const;
@@ -218,6 +230,11 @@ Returns a QPicture version of the item's icon, if available.
     virtual QPixmap iconPixmap() const;
 %Docstring
 Returns a QPixmap version of the item's icon, if available.
+%End
+
+    virtual void updateStoredComponentPosition( const QPointF &pos ) = 0;
+%Docstring
+Updates the position stored in the model for the associated comment
 %End
 
 };
@@ -264,6 +281,8 @@ Ownership of ``parameter`` is transferred to the item.
 
     virtual QPicture iconPicture() const;
 
+    virtual void updateStoredComponentPosition( const QPointF &pos );
+
 
   protected slots:
 
@@ -320,6 +339,8 @@ Ownership of ``child`` is transferred to the item.
 
     virtual QString linkPointText( Qt::Edge edge, int index ) const;
 
+    virtual void updateStoredComponentPosition( const QPointF &pos );
+
 
   protected slots:
 
@@ -368,6 +389,8 @@ Ownership of ``output`` is transferred to the item.
 
     virtual QPicture iconPicture() const;
 
+    virtual void updateStoredComponentPosition( const QPointF &pos );
+
 
   protected slots:
 
@@ -376,6 +399,62 @@ Ownership of ``output`` is transferred to the item.
 
 };
 
+
+
+class QgsModelCommentGraphicItem : QgsModelComponentGraphicItem
+{
+%Docstring
+A graphic item representing a model comment in the model designer.
+
+.. warning::
+
+   Not stable API
+
+.. versionadded:: 3.14
+%End
+
+%TypeHeaderCode
+#include "qgsmodelcomponentgraphicitem.h"
+%End
+  public:
+
+    QgsModelCommentGraphicItem( QgsProcessingModelComment *comment /Transfer/,
+                                QgsModelComponentGraphicItem *parentItem,
+                                QgsProcessingModelAlgorithm *model,
+                                QGraphicsItem *parent /TransferThis/ );
+%Docstring
+Constructor for QgsModelCommentGraphicItem for the specified ``comment``, with the specified ``parent`` item.
+
+The ``model`` argument specifies the associated processing model. Ownership of ``model`` is not transferred, and
+it must exist for the lifetime of this object.
+
+Ownership of ``output`` is transferred to the item.
+%End
+    ~QgsModelCommentGraphicItem();
+    virtual void contextMenuEvent( QGraphicsSceneContextMenuEvent *event );
+
+
+  protected:
+
+    virtual QColor fillColor( State state ) const;
+
+    virtual QColor strokeColor( State state ) const;
+
+    virtual QColor textColor( State state ) const;
+
+    virtual Qt::PenStyle strokeStyle( State state ) const;
+
+    virtual void updateStoredComponentPosition( const QPointF &pos );
+
+
+  protected slots:
+
+    virtual void deleteComponent();
+
+    virtual void editComponent();
+
+};
+
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *
diff --git a/python/gui/auto_generated/processing/models/qgsmodelgraphicsscene.sip.in b/python/gui/auto_generated/processing/models/qgsmodelgraphicsscene.sip.in
index 1a1dbe602cc..5c38ba7757e 100644
--- a/python/gui/auto_generated/processing/models/qgsmodelgraphicsscene.sip.in
+++ b/python/gui/auto_generated/processing/models/qgsmodelgraphicsscene.sip.in
@@ -110,6 +110,13 @@ Creates a new graphic item for a model child algorithm.
 Creates a new graphic item for a model output.
 %End
 
+    virtual QgsModelComponentGraphicItem *createCommentGraphicItem( QgsProcessingModelAlgorithm *model, QgsProcessingModelComment *comment,
+        QgsModelComponentGraphicItem *parentItem ) const /Factory/;
+%Docstring
+Creates a new graphic item for a model comment.
+%End
+
+
 };
 
 
diff --git a/python/plugins/processing/modeler/ModelerGraphicItem.py b/python/plugins/processing/modeler/ModelerGraphicItem.py
index 377985f0a82..53d6a8bd916 100644
--- a/python/plugins/processing/modeler/ModelerGraphicItem.py
+++ b/python/plugins/processing/modeler/ModelerGraphicItem.py
@@ -29,7 +29,8 @@ from qgis.gui import (
     QgsProcessingParameterWidgetContext,
     QgsModelParameterGraphicItem,
     QgsModelChildAlgorithmGraphicItem,
-    QgsModelOutputGraphicItem
+    QgsModelOutputGraphicItem,
+    QgsModelCommentGraphicItem
 )
 from processing.modeler.ModelerParameterDefinitionDialog import ModelerParameterDefinitionDialog
 from processing.modeler.ModelerParametersDialog import ModelerParametersDialog
@@ -59,15 +60,20 @@ class ModelerInputGraphicItem(QgsModelParameterGraphicItem):
         widget_context.setModel(self.model())
         return widget_context
 
-    def editComponent(self):
+    def edit(self, edit_comment=False):
         existing_param = self.model().parameterDefinition(self.component().parameterName())
+        comment = self.component().comment().description()
         new_param = None
         if ModelerParameterDefinitionDialog.use_legacy_dialog(param=existing_param):
             # boo, old api
             dlg = ModelerParameterDefinitionDialog(self.model(),
                                                    param=existing_param)
+            dlg.setComments(comment)
+            if edit_comment:
+                dlg.switchToCommentTab()
             if dlg.exec_():
                 new_param = dlg.param
+                comment = dlg.comments()
         else:
             # yay, use new API!
             context = createContext()
@@ -84,11 +90,18 @@ class ModelerInputGraphicItem(QgsModelParameterGraphicItem):
             self.model().removeModelParameter(self.component().parameterName())
             self.component().setParameterName(new_param.name())
             self.component().setDescription(new_param.name())
+            self.component().comment().setDescription(comment)
             self.model().addModelParameter(new_param, self.component())
             self.setLabel(new_param.description())
             self.requestModelRepaint.emit()
             self.changed.emit()
 
+    def editComponent(self):
+        self.edit()
+
+    def editComment(self):
+        self.edit(edit_comment=True)
+
 
 class ModelerChildAlgorithmGraphicItem(QgsModelChildAlgorithmGraphicItem):
     """
@@ -101,10 +114,13 @@ class ModelerChildAlgorithmGraphicItem(QgsModelChildAlgorithmGraphicItem):
     def __init__(self, element, model):
         super().__init__(element, model, None)
 
-    def editComponent(self):
+    def edit(self, edit_comment=False):
         elemAlg = self.component().algorithm()
         dlg = ModelerParametersDialog(elemAlg, self.model(), self.component().childId(),
                                       self.component().configuration())
+        dlg.setComments(self.component().comment().description())
+        if edit_comment:
+            dlg.switchToCommentTab()
         if dlg.exec_():
             alg = dlg.createAlgorithm()
             alg.setChildId(self.component().childId())
@@ -112,11 +128,18 @@ class ModelerChildAlgorithmGraphicItem(QgsModelChildAlgorithmGraphicItem):
             self.requestModelRepaint.emit()
             self.changed.emit()
 
+    def editComponent(self):
+        self.edit()
+
+    def editComment(self):
+        self.edit(edit_comment=True)
+
     def updateAlgorithm(self, alg):
         existing_child = self.model().childAlgorithm(alg.childId())
         alg.setPosition(existing_child.position())
         alg.setLinksCollapsed(Qt.TopEdge, existing_child.linksCollapsed(Qt.TopEdge))
         alg.setLinksCollapsed(Qt.BottomEdge, existing_child.linksCollapsed(Qt.BottomEdge))
+        alg.comment().setPosition(existing_child.comment().position())
         for i, out in enumerate(alg.modelOutputs().keys()):
             alg.modelOutput(out).setPosition(alg.modelOutput(out).position()
                                              or alg.position() + QPointF(
@@ -136,15 +159,42 @@ class ModelerOutputGraphicItem(QgsModelOutputGraphicItem):
     def __init__(self, element, model):
         super().__init__(element, model, None)
 
-    def editComponent(self):
+    def edit(self, edit_comment=False):
         child_alg = self.model().childAlgorithm(self.component().childId())
         param_name = '{}:{}'.format(self.component().childId(), self.component().name())
         dlg = ModelerParameterDefinitionDialog(self.model(),
                                                param=self.model().parameterDefinition(param_name))
-        if dlg.exec_() and dlg.param is not None:
+        dlg.setComments(self.component().comment().description())
+        if edit_comment:
+            dlg.switchToCommentTab()
+
+        if dlg.exec_():
             model_output = child_alg.modelOutput(self.component().name())
             model_output.setDescription(dlg.param.description())
             model_output.setDefaultValue(dlg.param.defaultValue())
             model_output.setMandatory(not (dlg.param.flags() & QgsProcessingParameterDefinition.FlagOptional))
+            model_output.comment().setDescription(dlg.comments())
             self.model().updateDestinationParameters()
+            self.requestModelRepaint.emit()
             self.changed.emit()
+
+    def editComponent(self):
+        self.edit()
+
+    def editComment(self):
+        self.edit(edit_comment=True)
+
+
+class ModelerCommentGraphicItem(QgsModelCommentGraphicItem):
+    """
+    IMPORTANT! This is intentionally a MINIMAL class, only containing code which HAS TO BE HERE
+    because it contains Python code for compatibility with deprecated methods ONLY.
+
+    Don't add anything here -- edit the c++ base class instead!
+    """
+
+    def __init__(self, model, element, parent_component):
+        super().__init__(element, parent_component, model, None)
+
+    def editComponent(self):
+        pass
diff --git a/python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py b/python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py
index c95a794ba5b..ce102384026 100755
--- a/python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py
+++ b/python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py
@@ -33,7 +33,10 @@ from qgis.PyQt.QtWidgets import (QDialog,
                                  QComboBox,
                                  QCheckBox,
                                  QDialogButtonBox,
-                                 QMessageBox)
+                                 QMessageBox,
+                                 QTabWidget,
+                                 QWidget,
+                                 QTextEdit)
 
 from qgis.gui import QgsExpressionLineEdit, QgsProjectionSelectionWidget
 from qgis.core import (QgsApplication,
@@ -124,13 +127,20 @@ class ModelerParameterDefinitionDialog(QDialog):
         settings.setValue("/Processing/modelParametersDefinitionDialogGeometry", self.saveGeometry())
         super(ModelerParameterDefinitionDialog, self).closeEvent(event)
 
+    def switchToCommentTab(self):
+        self.tab.setCurrentIndex(1)
+
     def setupUi(self):
         type_metadata = QgsApplication.processingRegistry().parameterType(self.param.type() if self.param else self.paramType)
         self.setWindowTitle(self.tr('{} Parameter Definition').format(type_metadata.name()))
+
+        self.mainLayout = QVBoxLayout()
+        self.tab = QTabWidget()
+        self.mainLayout.addWidget(self.tab)
+
         self.setMinimumWidth(300)
 
-        self.verticalLayout = QVBoxLayout(self)
-        self.verticalLayout.setMargin(20)
+        self.verticalLayout = QVBoxLayout()
 
         self.label = QLabel(self.tr('Parameter name'))
         self.verticalLayout.addWidget(self.label)
@@ -214,8 +224,8 @@ class ModelerParameterDefinitionDialog(QDialog):
             if self.param is not None:
                 self.shapetypeCombo.setCurrentIndex(self.shapetypeCombo.findData(self.param.dataTypes()[0]))
             self.verticalLayout.addWidget(self.shapetypeCombo)
-        elif (self.paramType == parameters.PARAMETER_MULTIPLE or
-              isinstance(self.param, QgsProcessingParameterMultipleLayers)):
+        elif (self.paramType == parameters.PARAMETER_MULTIPLE
+              or isinstance(self.param, QgsProcessingParameterMultipleLayers)):
             self.verticalLayout.addWidget(QLabel(self.tr('Data type')))
             self.datatypeCombo = QComboBox()
             self.datatypeCombo.addItem(self.tr('Any Map Layer'), QgsProcessing.TypeMapLayer)
@@ -229,11 +239,11 @@ class ModelerParameterDefinitionDialog(QDialog):
             if self.param is not None:
                 self.datatypeCombo.setCurrentIndex(self.datatypeCombo.findData(self.param.layerType()))
             self.verticalLayout.addWidget(self.datatypeCombo)
-        elif (self.paramType in (parameters.PARAMETER_NUMBER, parameters.PARAMETER_DISTANCE, parameters.PARAMETER_SCALE) or
-              isinstance(self.param, (QgsProcessingParameterNumber, QgsProcessingParameterDistance, QgsProcessingParameterScale))):
+        elif (self.paramType in (parameters.PARAMETER_NUMBER, parameters.PARAMETER_DISTANCE, parameters.PARAMETER_SCALE)
+              or isinstance(self.param, (QgsProcessingParameterNumber, QgsProcessingParameterDistance, QgsProcessingParameterScale))):
 
-            if (self.paramType == parameters.PARAMETER_DISTANCE or
-                    isinstance(self.param, QgsProcessingParameterDistance)):
+            if (self.paramType == parameters.PARAMETER_DISTANCE
+                    or isinstance(self.param, QgsProcessingParameterDistance)):
                 self.verticalLayout.addWidget(QLabel(self.tr('Linked input')))
                 self.parentCombo = QComboBox()
                 self.parentCombo.addItem('', '')
@@ -281,8 +291,8 @@ class ModelerParameterDefinitionDialog(QDialog):
                 if default:
                     self.defaultTextBox.setText(str(default))
             self.verticalLayout.addWidget(self.defaultTextBox)
-        elif (self.paramType == parameters.PARAMETER_EXPRESSION or
-              isinstance(self.param, QgsProcessingParameterExpression)):
+        elif (self.paramType == parameters.PARAMETER_EXPRESSION
+              or isinstance(self.param, QgsProcessingParameterExpression)):
             self.verticalLayout.addWidget(QLabel(self.tr('Default value')))
             self.defaultEdit = QgsExpressionLineEdit()
             if self.param is not None:
@@ -302,15 +312,15 @@ class ModelerParameterDefinitionDialog(QDialog):
                             self.parentCombo.setCurrentIndex(idx)
                     idx += 1
             self.verticalLayout.addWidget(self.parentCombo)
-        elif (self.paramType == parameters.PARAMETER_POINT or
-              isinstance(self.param, QgsProcessingParameterPoint)):
+        elif (self.paramType == parameters.PARAMETER_POINT
+              or isinstance(self.param, QgsProcessingParameterPoint)):
             self.verticalLayout.addWidget(QLabel(self.tr('Default value')))
             self.defaultTextBox = QLineEdit()
             if self.param is not None:
                 self.defaultTextBox.setText(self.param.defaultValue())
             self.verticalLayout.addWidget(self.defaultTextBox)
-        elif (self.paramType == parameters.PARAMETER_CRS or
-              isinstance(self.param, QgsProcessingParameterCrs)):
+        elif (self.paramType == parameters.PARAMETER_CRS
+              or isinstance(self.param, QgsProcessingParameterCrs)):
             self.verticalLayout.addWidget(QLabel(self.tr('Default value')))
             self.selector = QgsProjectionSelectionWidget()
             if self.param is not None:
@@ -367,18 +377,37 @@ class ModelerParameterDefinitionDialog(QDialog):
             self.advancedCheck.setEnabled(False)
             self.advancedCheck.setChecked(False)
 
+        self.verticalLayout.addStretch()
+
+        w = QWidget()
+        w.setLayout(self.verticalLayout)
+        self.tab.addTab(w, self.tr('Properties'))
+
+        self.commentLayout = QVBoxLayout()
+        self.commentEdit = QTextEdit()
+        self.commentEdit.setAcceptRichText(False)
+        self.commentLayout.addWidget(self.commentEdit)
+        w2 = QWidget()
+        w2.setLayout(self.commentLayout)
+        self.tab.addTab(w2, self.tr('Comments'))
+
         self.buttonBox = QDialogButtonBox(self)
         self.buttonBox.setOrientation(Qt.Horizontal)
-        self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel |
-                                          QDialogButtonBox.Ok)
+        self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel
+                                          | QDialogButtonBox.Ok)
         self.buttonBox.setObjectName('buttonBox')
         self.buttonBox.accepted.connect(self.accept)
         self.buttonBox.rejected.connect(self.reject)
 
-        self.verticalLayout.addStretch()
-        self.verticalLayout.addWidget(self.buttonBox)
+        self.mainLayout.addWidget(self.buttonBox)
 
-        self.setLayout(self.verticalLayout)
+        self.setLayout(self.mainLayout)
+
+    def setComments(self, text):
+        self.commentEdit.setPlainText(text)
+
+    def comments(self):
+        return self.commentEdit.toPlainText()
 
     def accept(self):
         description = self.nameTextBox.text()
@@ -397,8 +426,8 @@ class ModelerParameterDefinitionDialog(QDialog):
                 i += 1
         else:
             name = self.param.name()
-        if (self.paramType == parameters.PARAMETER_TABLE_FIELD or
-                isinstance(self.param, QgsProcessingParameterField)):
+        if (self.paramType == parameters.PARAMETER_TABLE_FIELD
+                or isinstance(self.param, QgsProcessingParameterField)):
             if self.parentCombo.currentIndex() < 0:
                 QMessageBox.warning(self, self.tr('Unable to define parameter'),
                                     self.tr('Wrong or missing parameter values'))
@@ -411,39 +440,39 @@ class ModelerParameterDefinitionDialog(QDialog):
             self.param = QgsProcessingParameterField(name, description, defaultValue=default,
                                                      parentLayerParameterName=parent, type=datatype,
                                                      allowMultiple=self.multipleCheck.isChecked())
-        elif (self.paramType == parameters.PARAMETER_BAND or
-              isinstance(self.param, QgsProcessingParameterBand)):
+        elif (self.paramType == parameters.PARAMETER_BAND
+              or isinstance(self.param, QgsProcessingParameterBand)):
             if self.parentCombo.currentIndex() < 0:
                 QMessageBox.warning(self, self.tr('Unable to define parameter'),
                                     self.tr('Wrong or missing parameter values'))
                 return
             parent = self.parentCombo.currentData()
             self.param = QgsProcessingParameterBand(name, description, None, parent)
-        elif (self.paramType == parameters.PARAMETER_MAP_LAYER or
-              isinstance(self.param, QgsProcessingParameterMapLayer)):
+        elif (self.paramType == parameters.PARAMETER_MAP_LAYER
+              or isinstance(self.param, QgsProcessingParameterMapLayer)):
             self.param = QgsProcessingParameterMapLayer(
                 name, description)
-        elif (self.paramType == parameters.PARAMETER_RASTER or
-              isinstance(self.param, QgsProcessingParameterRasterLayer)):
+        elif (self.paramType == parameters.PARAMETER_RASTER
+              or isinstance(self.param, QgsProcessingParameterRasterLayer)):
             self.param = QgsProcessingParameterRasterLayer(
                 name, description)
-        elif (self.paramType == parameters.PARAMETER_TABLE or
-              isinstance(self.param, QgsProcessingParameterVectorLayer)):
+        elif (self.paramType == parameters.PARAMETER_TABLE
+              or isinstance(self.param, QgsProcessingParameterVectorLayer)):
             self.param = QgsProcessingParameterVectorLayer(
                 name, description,
                 [self.shapetypeCombo.currentData()])
-        elif (self.paramType == parameters.PARAMETER_VECTOR or
-              isinstance(self.param, QgsProcessingParameterFeatureSource)):
+        elif (self.paramType == parameters.PARAMETER_VECTOR
+              or isinstance(self.param, QgsProcessingParameterFeatureSource)):
             self.param = QgsProcessingParameterFeatureSource(
                 name, description,
                 [self.shapetypeCombo.currentData()])
-        elif (self.paramType == parameters.PARAMETER_MULTIPLE or
-              isinstance(self.param, QgsProcessingParameterMultipleLayers)):
+        elif (self.paramType == parameters.PARAMETER_MULTIPLE
+              or isinstance(self.param, QgsProcessingParameterMultipleLayers)):
             self.param = QgsProcessingParameterMultipleLayers(
                 name, description,
                 self.datatypeCombo.currentData())
-        elif (self.paramType == parameters.PARAMETER_DISTANCE or
-              isinstance(self.param, QgsProcessingParameterDistance)):
+        elif (self.paramType == parameters.PARAMETER_DISTANCE
+              or isinstance(self.param, QgsProcessingParameterDistance)):
             self.param = QgsProcessingParameterDistance(name, description,
                                                         self.defaultTextBox.text())
             try:
@@ -465,12 +494,12 @@ class ModelerParameterDefinitionDialog(QDialog):
             parent = self.parentCombo.currentData()
             if parent:
                 self.param.setParentParameterName(parent)
-        elif (self.paramType == parameters.PARAMETER_SCALE or
-              isinstance(self.param, QgsProcessingParameterScale)):
+        elif (self.paramType == parameters.PARAMETER_SCALE
+              or isinstance(self.param, QgsProcessingParameterScale)):
             self.param = QgsProcessingParameterScale(name, description,
                                                      self.defaultTextBox.text())
-        elif (self.paramType == parameters.PARAMETER_NUMBER or
-              isinstance(self.param, QgsProcessingParameterNumber)):
+        elif (self.paramType == parameters.PARAMETER_NUMBER
+              or isinstance(self.param, QgsProcessingParameterNumber)):
 
             type = self.type_combo.currentData()
             self.param = QgsProcessingParameterNumber(name, description, type,
@@ -486,27 +515,27 @@ class ModelerParameterDefinitionDialog(QDialog):
                 QMessageBox.warning(self, self.tr('Unable to define parameter'),
                                     self.tr('Wrong or missing parameter values'))
                 return
-        elif (self.paramType == parameters.PARAMETER_EXPRESSION or
-              isinstance(self.param, QgsProcessingParameterExpression)):
+        elif (self.paramType == parameters.PARAMETER_EXPRESSION
+              or isinstance(self.param, QgsProcessingParameterExpression)):
             parent = self.parentCombo.currentData()
             self.param = QgsProcessingParameterExpression(name, description,
                                                           str(self.defaultEdit.expression()),
                                                           parent)
-        elif (self.paramType == parameters.PARAMETER_EXTENT or
-              isinstance(self.param, QgsProcessingParameterExtent)):
+        elif (self.paramType == parameters.PARAMETER_EXTENT
+              or isinstance(self.param, QgsProcessingParameterExtent)):
             self.param = QgsProcessingParameterExtent(name, description)
-        elif (self.paramType == parameters.PARAMETER_POINT or
-              isinstance(self.param, QgsProcessingParameterPoint)):
+        elif (self.paramType == parameters.PARAMETER_POINT
+              or isinstance(self.param, QgsProcessingParameterPoint)):
             self.param = QgsProcessingParameterPoint(name, description,
                                                      str(self.defaultTextBox.text()))
-        elif (self.paramType == parameters.PARAMETER_CRS or
-              isinstance(self.param, QgsProcessingParameterCrs)):
+        elif (self.paramType == parameters.PARAMETER_CRS
+              or isinstance(self.param, QgsProcessingParameterCrs)):
             self.param = QgsProcessingParameterCrs(name, description, self.selector.crs().authid())
-        elif (self.paramType == parameters.PARAMETER_ENUM or
-                isinstance(self.param, QgsProcessingParameterEnum)):
+        elif (self.paramType == parameters.PARAMETER_ENUM
+                or isinstance(self.param, QgsProcessingParameterEnum)):
             self.param = QgsProcessingParameterEnum(name, description, self.widget.options(), self.widget.allowMultiple(), self.widget.defaultOptions())
-        elif (self.paramType == parameters.PARAMETER_MATRIX or
-                isinstance(self.param, QgsProcessingParameterMatrix)):
+        elif (self.paramType == parameters.PARAMETER_MATRIX
+                or isinstance(self.param, QgsProcessingParameterMatrix)):
             self.param = QgsProcessingParameterMatrix(name, description, hasFixedNumberRows=self.widget.fixedRows(), headers=self.widget.headers(), defaultValue=self.widget.value())
 
         # Destination parameter
diff --git a/python/plugins/processing/modeler/ModelerParametersDialog.py b/python/plugins/processing/modeler/ModelerParametersDialog.py
index bcea2f5157f..81aaed815da 100644
--- a/python/plugins/processing/modeler/ModelerParametersDialog.py
+++ b/python/plugins/processing/modeler/ModelerParametersDialog.py
@@ -29,7 +29,7 @@ from qgis.PyQt.QtCore import (Qt,
                               QByteArray)
 from qgis.PyQt.QtWidgets import (QDialog, QDialogButtonBox, QLabel, QLineEdit,
                                  QFrame, QPushButton, QSizePolicy, QVBoxLayout,
-                                 QHBoxLayout, QWidget)
+                                 QHBoxLayout, QWidget, QTabWidget, QTextEdit)
 
 from qgis.core import (Qgis,
                        QgsProject,
@@ -102,6 +102,9 @@ class ModelerParametersDialog(QDialog):
         settings.setValue("/Processing/modelParametersDialogGeometry", self.saveGeometry())
         super(ModelerParametersDialog, self).closeEvent(event)
 
+    def switchToCommentTab(self):
+        self.tab.setCurrentIndex(1)
+
     def setupUi(self):
         self.checkBoxes = {}
         self.showAdvanced = False
@@ -111,6 +114,11 @@ class ModelerParametersDialog(QDialog):
         self.algorithmItem = None
 
         self.resize(650, 450)
+
+        self.mainLayout = QVBoxLayout()
+        self.tab = QTabWidget()
+        self.mainLayout.addWidget(self.tab)
+
         self.buttonBox = QDialogButtonBox()
         self.buttonBox.setOrientation(Qt.Horizontal)
         self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel | QDialogButtonBox.Ok | QDialogButtonBox.Help)
@@ -118,7 +126,6 @@ class ModelerParametersDialog(QDialog):
                            QSizePolicy.Expanding)
         self.verticalLayout = QVBoxLayout()
         self.verticalLayout.setSpacing(5)
-        self.verticalLayout.setMargin(20)
 
         self.bar = QgsMessageBar()
         self.bar.setSizePolicy(QSizePolicy.Minimum, QSizePolicy.Fixed)
@@ -229,13 +236,33 @@ class ModelerParametersDialog(QDialog):
         self.scrollArea.setWidgetResizable(True)
 
         self.verticalLayout2.addWidget(self.scrollArea)
-        self.verticalLayout2.addWidget(self.buttonBox)
-        self.setLayout(self.verticalLayout2)
         self.buttonBox.accepted.connect(self.okPressed)
         self.buttonBox.rejected.connect(self.cancelPressed)
         self.buttonBox.helpRequested.connect(self.openHelp)
+
+        w = QWidget()
+        w.setLayout(self.verticalLayout2)
+        self.tab.addTab(w, self.tr('Properties'))
+
+        self.commentLayout = QVBoxLayout()
+        self.commentEdit = QTextEdit()
+        self.commentEdit.setAcceptRichText(False)
+        self.commentLayout.addWidget(self.commentEdit)
+        w2 = QWidget()
+        w2.setLayout(self.commentLayout)
+        self.tab.addTab(w2, self.tr('Comments'))
+
+        self.mainLayout.addWidget(self.buttonBox)
+        self.setLayout(self.mainLayout)
+
         QMetaObject.connectSlotsByName(self)
 
+    def setComments(self, text):
+        self.commentEdit.setPlainText(text)
+
+    def comments(self):
+        return self.commentEdit.toPlainText()
+
     def getAvailableDependencies(self):  # spellok
         if self.childId is None:
             dependent = []
@@ -378,9 +405,9 @@ class ModelerParametersDialog(QDialog):
                     [isinstance(subval, QgsProcessingModelChildParameterSource) for subval in val])):
                 val = [QgsProcessingModelChildParameterSource.fromStaticValue(val)]
             for subval in val:
-                if (isinstance(subval, QgsProcessingModelChildParameterSource) and
-                    subval.source() == QgsProcessingModelChildParameterSource.StaticValue and
-                        not param.checkValueIsAcceptable(subval.staticValue())) \
+                if (isinstance(subval, QgsProcessingModelChildParameterSource)
+                    and subval.source() == QgsProcessingModelChildParameterSource.StaticValue
+                        and not param.checkValueIsAcceptable(subval.staticValue())) \
                         or (subval is None and not param.flags() & QgsProcessingParameterDefinition.FlagOptional):
                     self.bar.pushMessage(self.tr("Error"), self.tr("Wrong or missing value for parameter '{}'").format(
                         param.description()),
@@ -419,6 +446,7 @@ class ModelerParametersDialog(QDialog):
         #except:
         #    pass
 
+        alg.comment().setDescription(self.comments())
         return alg
 
     def okPressed(self):
diff --git a/python/plugins/processing/modeler/ModelerScene.py b/python/plugins/processing/modeler/ModelerScene.py
index dd5b3352289..aaf1acc078f 100644
--- a/python/plugins/processing/modeler/ModelerScene.py
+++ b/python/plugins/processing/modeler/ModelerScene.py
@@ -25,7 +25,8 @@ from qgis.gui import QgsModelGraphicsScene
 from processing.modeler.ModelerGraphicItem import (
     ModelerInputGraphicItem,
     ModelerOutputGraphicItem,
-    ModelerChildAlgorithmGraphicItem
+    ModelerChildAlgorithmGraphicItem,
+    ModelerCommentGraphicItem
 )
 
 
@@ -48,3 +49,6 @@ class ModelerScene(QgsModelGraphicsScene):
 
     def createOutputGraphicItem(self, model, output):
         return ModelerOutputGraphicItem(output.clone(), model)
+
+    #def createCommentGraphicItem(self, model, comment, parent):
+    #    return ModelerCommentGraphicItem(model, comment.clone(), parent)
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 24f0a88c643..127670642aa 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -152,6 +152,7 @@ SET(QGIS_CORE_SRCS
   processing/models/qgsprocessingmodelalgorithm.cpp
   processing/models/qgsprocessingmodelchildalgorithm.cpp
   processing/models/qgsprocessingmodelchildparametersource.cpp
+  processing/models/qgsprocessingmodelcomment.cpp
   processing/models/qgsprocessingmodelcomponent.cpp
   processing/models/qgsprocessingmodelparameter.cpp
   processing/models/qgsprocessingmodeloutput.cpp
@@ -1169,6 +1170,7 @@ SET(QGIS_CORE_HDRS
   processing/models/qgsprocessingmodelalgorithm.h
   processing/models/qgsprocessingmodelchildalgorithm.h
   processing/models/qgsprocessingmodelchildparametersource.h
+  processing/models/qgsprocessingmodelcomment.h
   processing/models/qgsprocessingmodelcomponent.h
   processing/models/qgsprocessingmodeloutput.h
   processing/models/qgsprocessingmodelparameter.h
diff --git a/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp b/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
index 92d27a83db5..f385c606946 100644
--- a/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
+++ b/src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp
@@ -35,6 +35,7 @@ QgsProcessingModelChildAlgorithm::QgsProcessingModelChildAlgorithm( const QgsPro
   , mModelOutputs( other.mModelOutputs )
   , mActive( other.mActive )
   , mDependencies( other.mDependencies )
+  , mComment( other.mComment )
 {
   setAlgorithmId( other.algorithmId() );
 }
@@ -49,6 +50,7 @@ QgsProcessingModelChildAlgorithm &QgsProcessingModelChildAlgorithm::operator=( c
   mModelOutputs = other.mModelOutputs;
   mActive = other.mActive;
   mDependencies = other.mDependencies;
+  mComment = other.mComment;
   return *this;
 }
 
@@ -89,6 +91,7 @@ QVariant QgsProcessingModelChildAlgorithm::toVariant() const
   map.insert( QStringLiteral( "alg_config" ), mConfiguration );
   map.insert( QStringLiteral( "active" ), mActive );
   map.insert( QStringLiteral( "dependencies" ), mDependencies );
+  map.insert( QStringLiteral( "comment" ), mComment.toVariant() );
 
   saveCommonProperties( map );
 
@@ -126,6 +129,7 @@ bool QgsProcessingModelChildAlgorithm::loadVariant( const QVariant &child )
   setAlgorithmId( map.value( QStringLiteral( "alg_id" ) ).toString() );
   mActive = map.value( QStringLiteral( "active" ) ).toBool();
   mDependencies = map.value( QStringLiteral( "dependencies" ) ).toStringList();
+  mComment.loadVariant( map.value( QStringLiteral( "comment" ) ).toMap() );
 
   restoreCommonProperties( map );
 
diff --git a/src/core/processing/models/qgsprocessingmodelchildalgorithm.h b/src/core/processing/models/qgsprocessingmodelchildalgorithm.h
index aa0b17b28ed..63cfbeda68b 100644
--- a/src/core/processing/models/qgsprocessingmodelchildalgorithm.h
+++ b/src/core/processing/models/qgsprocessingmodelchildalgorithm.h
@@ -23,6 +23,7 @@
 #include "qgsprocessingmodelcomponent.h"
 #include "qgsprocessingmodelchildparametersource.h"
 #include "qgsprocessingmodeloutput.h"
+#include "qgsprocessingmodelcomment.h"
 #include <memory>
 
 class QgsProcessingModelAlgorithm;
@@ -261,6 +262,10 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
     QStringList asPythonCode( QgsProcessing::PythonOutputType outputType, const QgsStringMap &extraParameters, int currentIndent, int indentSize,
                               const QMap<QString, QString> &friendlyChildNames, const QMap<QString, QString> &friendlyOutputNames ) const;
 
+    SIP_SKIP const QgsProcessingModelComment *comment() const override { return &mComment; }
+    QgsProcessingModelComment *comment() override { return &mComment; }
+    void setComment( const QgsProcessingModelComment &comment ) override { mComment = comment; }
+
   private:
 
     QString mId;
@@ -281,6 +286,8 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
     //! List of child algorithms from the parent model on which this algorithm is dependent
     QStringList mDependencies;
 
+    QgsProcessingModelComment mComment;
+
     friend class TestQgsProcessing;
 
 };
diff --git a/src/core/processing/models/qgsprocessingmodelcomment.cpp b/src/core/processing/models/qgsprocessingmodelcomment.cpp
new file mode 100644
index 00000000000..d003803d056
--- /dev/null
+++ b/src/core/processing/models/qgsprocessingmodelcomment.cpp
@@ -0,0 +1,47 @@
+/***************************************************************************
+                         qgsprocessingmodelcomment.cpp
+                         --------------------------
+    begin                : February 2020
+    copyright            : (C) 2020 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsprocessingmodelcomment.h"
+
+///@cond NOT_STABLE
+
+QgsProcessingModelComment::QgsProcessingModelComment( const QString &description )
+  : QgsProcessingModelComponent( description )
+{
+  setSize( QSizeF( 100, 60 ) );
+}
+
+QgsProcessingModelComment *QgsProcessingModelComment::clone() const
+{
+  return new QgsProcessingModelComment( *this );
+}
+
+QVariant QgsProcessingModelComment::toVariant() const
+{
+  QVariantMap map;
+  saveCommonProperties( map );
+  return map;
+}
+
+bool QgsProcessingModelComment::loadVariant( const QVariantMap &map )
+{
+  restoreCommonProperties( map );
+  return true;
+}
+
+
+///@endcond
diff --git a/src/core/processing/models/qgsprocessingmodelcomment.h b/src/core/processing/models/qgsprocessingmodelcomment.h
new file mode 100644
index 00000000000..f5e2d155668
--- /dev/null
+++ b/src/core/processing/models/qgsprocessingmodelcomment.h
@@ -0,0 +1,59 @@
+/***************************************************************************
+                         qgsprocessingmodelcomment.h
+                         --------------------------
+    begin                : February 2020
+    copyright            : (C) 2020 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSPROCESSINGMODELCOMMENT_H
+#define QGSPROCESSINGMODELCOMMENT_H
+
+#include "qgis_core.h"
+#include "qgis.h"
+#include "qgsprocessingmodelcomponent.h"
+#include "qgsprocessingparameters.h"
+
+///@cond NOT_STABLE
+
+/**
+ * Represents a comment in a model.
+ * \ingroup core
+ * \since QGIS 3.14
+ */
+class CORE_EXPORT QgsProcessingModelComment : public QgsProcessingModelComponent
+{
+  public:
+
+    /**
+     * Constructor for QgsProcessingModelComment with the specified \a description.
+     */
+    QgsProcessingModelComment( const QString &description = QString() );
+
+    QgsProcessingModelComment *clone() const override SIP_FACTORY;
+
+    /**
+     * Saves this comment to a QVariant.
+     * \see loadVariant()
+     */
+    QVariant toVariant() const;
+
+    /**
+     * Loads this comment from a QVariantMap.
+     * \see toVariant()
+     */
+    bool loadVariant( const QVariantMap &map );
+};
+
+///@endcond
+
+#endif // QGSPROCESSINGMODELCOMMENT_H
diff --git a/src/core/processing/models/qgsprocessingmodelcomponent.cpp b/src/core/processing/models/qgsprocessingmodelcomponent.cpp
index 723261f78e4..f6d00136038 100644
--- a/src/core/processing/models/qgsprocessingmodelcomponent.cpp
+++ b/src/core/processing/models/qgsprocessingmodelcomponent.cpp
@@ -88,6 +88,11 @@ void QgsProcessingModelComponent::setLinksCollapsed( Qt::Edge edge, bool collaps
   }
 }
 
+void QgsProcessingModelComponent::setComment( const QgsProcessingModelComment & )
+{
+
+}
+
 void QgsProcessingModelComponent::saveCommonProperties( QVariantMap &map ) const
 {
   map.insert( QStringLiteral( "component_pos_x" ), mPosition.x() );
diff --git a/src/core/processing/models/qgsprocessingmodelcomponent.h b/src/core/processing/models/qgsprocessingmodelcomponent.h
index 51acdfbd27f..38dc49e23d2 100644
--- a/src/core/processing/models/qgsprocessingmodelcomponent.h
+++ b/src/core/processing/models/qgsprocessingmodelcomponent.h
@@ -23,6 +23,8 @@
 #include <QPointF>
 #include <QSizeF>
 
+class QgsProcessingModelComment;
+
 ///@cond NOT_STABLE
 
 /**
@@ -87,6 +89,24 @@ class CORE_EXPORT QgsProcessingModelComponent
      */
     void setLinksCollapsed( Qt::Edge edge, bool collapsed );
 
+    /**
+     * Returns the comment attached to this component (may be NULLPTR)
+     * \see setComment()
+     */
+    SIP_SKIP virtual const QgsProcessingModelComment *comment() const { return nullptr; }
+
+    /**
+     * Returns the comment attached to this component (may be NULLPTR)
+     * \see setComment()
+     */
+    virtual QgsProcessingModelComment *comment() { return nullptr; }
+
+    /**
+     * Sets the \a comment attached to this component.
+     * \see comment()
+     */
+    virtual void setComment( const QgsProcessingModelComment &comment );
+
     /**
      * Clones the component.
      *
diff --git a/src/core/processing/models/qgsprocessingmodeloutput.cpp b/src/core/processing/models/qgsprocessingmodeloutput.cpp
index 18bddc85f35..a5eaa357f33 100644
--- a/src/core/processing/models/qgsprocessingmodeloutput.cpp
+++ b/src/core/processing/models/qgsprocessingmodeloutput.cpp
@@ -48,6 +48,7 @@ QVariant QgsProcessingModelOutput::toVariant() const
   map.insert( QStringLiteral( "child_id" ), mChildId );
   map.insert( QStringLiteral( "output_name" ), mOutputName );
   map.insert( QStringLiteral( "mandatory" ), mMandatory );
+  map.insert( QStringLiteral( "comment" ), mComment.toVariant() );
   saveCommonProperties( map );
   return map;
 }
@@ -79,6 +80,7 @@ bool QgsProcessingModelOutput::loadVariant( const QVariantMap &map )
   mChildId = map.value( QStringLiteral( "child_id" ) ).toString();
   mOutputName = map.value( QStringLiteral( "output_name" ) ).toString();
   mMandatory = map.value( QStringLiteral( "mandatory" ), false ).toBool();
+  mComment.loadVariant( map.value( QStringLiteral( "comment" ) ).toMap() );
   restoreCommonProperties( map );
   return true;
 }
diff --git a/src/core/processing/models/qgsprocessingmodeloutput.h b/src/core/processing/models/qgsprocessingmodeloutput.h
index 1e2541d9f87..f64b6905ee1 100644
--- a/src/core/processing/models/qgsprocessingmodeloutput.h
+++ b/src/core/processing/models/qgsprocessingmodeloutput.h
@@ -22,6 +22,7 @@
 #include "qgis.h"
 #include "qgsprocessingmodelcomponent.h"
 #include "qgsprocessingparameters.h"
+#include "qgsprocessingmodelcomment.h"
 
 ///@cond NOT_STABLE
 
@@ -121,6 +122,10 @@ class CORE_EXPORT QgsProcessingModelOutput : public QgsProcessingModelComponent
      */
     bool loadVariant( const QVariantMap &map );
 
+    SIP_SKIP const QgsProcessingModelComment *comment() const override { return &mComment; }
+    QgsProcessingModelComment *comment() override { return &mComment; }
+    void setComment( const QgsProcessingModelComment &comment ) override { mComment = comment; }
+
   private:
 
     QString mName;
@@ -128,6 +133,9 @@ class CORE_EXPORT QgsProcessingModelOutput : public QgsProcessingModelComponent
     QString mChildId;
     QString mOutputName;
     bool mMandatory = false;
+
+    QgsProcessingModelComment mComment;
+
 };
 
 ///@endcond
diff --git a/src/core/processing/models/qgsprocessingmodelparameter.cpp b/src/core/processing/models/qgsprocessingmodelparameter.cpp
index b721dcfa8b3..4cd52cafa59 100644
--- a/src/core/processing/models/qgsprocessingmodelparameter.cpp
+++ b/src/core/processing/models/qgsprocessingmodelparameter.cpp
@@ -34,6 +34,7 @@ QVariant QgsProcessingModelParameter::toVariant() const
 {
   QVariantMap map;
   map.insert( QStringLiteral( "name" ), mParameterName );
+  map.insert( QStringLiteral( "comment" ), mComment.toVariant() );
   saveCommonProperties( map );
   return map;
 }
@@ -41,6 +42,7 @@ QVariant QgsProcessingModelParameter::toVariant() const
 bool QgsProcessingModelParameter::loadVariant( const QVariantMap &map )
 {
   mParameterName = map.value( QStringLiteral( "name" ) ).toString();
+  mComment.loadVariant( map.value( QStringLiteral( "comment" ) ).toMap() );
   restoreCommonProperties( map );
   return true;
 }
diff --git a/src/core/processing/models/qgsprocessingmodelparameter.h b/src/core/processing/models/qgsprocessingmodelparameter.h
index 6b54d346be1..f6d63973e35 100644
--- a/src/core/processing/models/qgsprocessingmodelparameter.h
+++ b/src/core/processing/models/qgsprocessingmodelparameter.h
@@ -21,6 +21,7 @@
 #include "qgis_core.h"
 #include "qgis.h"
 #include "qgsprocessingmodelcomponent.h"
+#include "qgsprocessingmodelcomment.h"
 
 ///@cond NOT_STABLE
 
@@ -68,10 +69,16 @@ class CORE_EXPORT QgsProcessingModelParameter : public QgsProcessingModelCompone
      */
     bool loadVariant( const QVariantMap &map );
 
+    SIP_SKIP const QgsProcessingModelComment *comment() const override { return &mComment; }
+    QgsProcessingModelComment *comment() override { return &mComment; }
+    void setComment( const QgsProcessingModelComment &comment ) override { mComment = comment; }
+
   private:
 
     QString mParameterName;
 
+    QgsProcessingModelComment mComment;
+
 };
 
 ///@endcond
diff --git a/src/core/qgsxmlutils.cpp b/src/core/qgsxmlutils.cpp
index a3e0ce0ef29..13d32b59455 100644
--- a/src/core/qgsxmlutils.cpp
+++ b/src/core/qgsxmlutils.cpp
@@ -20,6 +20,7 @@
 #include "qgsrectangle.h"
 #include "qgsproperty.h"
 #include "qgssymbollayerutils.h"
+#include "qgsprocessingparameters.h"
 
 QgsUnitTypes::DistanceUnit QgsXmlUtils::readMapUnits( const QDomElement &element )
 {
@@ -213,7 +214,15 @@ QDomElement QgsXmlUtils::writeVariant( const QVariant &value, QDomDocument &doc
         element.setAttribute( QStringLiteral( "value" ), geom.asWkt() );
         break;
       }
-      FALLTHROUGH
+      else if ( value.canConvert< QgsProcessingOutputLayerDefinition >() )
+      {
+        QDomElement valueElement = writeVariant( value.value< QgsProcessingOutputLayerDefinition >().toVariant(), doc );
+        element.appendChild( valueElement );
+        element.setAttribute( QStringLiteral( "type" ), QStringLiteral( "QgsProcessingOutputLayerDefinition" ) );
+        break;
+      }
+      Q_ASSERT_X( false, "QgsXmlUtils::writeVariant", QStringLiteral( "unsupported user variant type %1" ).arg( QMetaType::typeName( value.userType() ) ).toLocal8Bit() );
+      break;
     }
 
     default:
@@ -338,6 +347,18 @@ QVariant QgsXmlUtils::readVariant( const QDomElement &element )
   {
     return QgsGeometry::fromWkt( element.attribute( "value" ) );
   }
+  else if ( type == QLatin1String( "QgsProcessingOutputLayerDefinition" ) )
+  {
+    QgsProcessingOutputLayerDefinition res;
+    const QDomNodeList values = element.childNodes();
+    if ( values.isEmpty() )
+      return QVariant();
+
+    if ( res.loadVariant( QgsXmlUtils::readVariant( values.at( 0 ).toElement() ).toMap() ) )
+      return res;
+
+    return QVariant();
+  }
   else
   {
     return QVariant();
diff --git a/src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp b/src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp
index 933ff21fdbb..898ddbf39bb 100644
--- a/src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp
+++ b/src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp
@@ -131,14 +131,7 @@ QVariant QgsModelComponentGraphicItem::itemChange( QGraphicsItem::GraphicsItemCh
       mComponent->setPosition( pos() );
 
       // also need to update the model's stored component's position
-      // TODO - this is not so nice, consider moving this to model class
-      if ( QgsProcessingModelChildAlgorithm *child = dynamic_cast< QgsProcessingModelChildAlgorithm * >( mComponent.get() ) )
-        mModel->childAlgorithm( child->childId() ).setPosition( pos() );
-      else if ( QgsProcessingModelParameter *param = dynamic_cast< QgsProcessingModelParameter * >( mComponent.get() ) )
-        mModel->parameterComponent( param->parameterName() ).setPosition( pos() );
-      else if ( QgsProcessingModelOutput *output = dynamic_cast< QgsProcessingModelOutput * >( mComponent.get() ) )
-        mModel->childAlgorithm( output->childId() ).modelOutput( output->name() ).setPosition( pos() );
-
+      updateStoredComponentPosition( pos() );
       break;
     }
     case QGraphicsItem::ItemSelectedChange:
@@ -197,7 +190,9 @@ void QgsModelComponentGraphicItem::paint( QPainter *painter, const QStyleOptionG
   QColor color = fillColor( state() );
   QColor stroke = strokeColor( state() );
 
-  painter->setPen( QPen( stroke, 0 ) ); // 0 width "cosmetic" pen
+  QPen strokePen = QPen( stroke, 0 ) ; // 0 width "cosmetic" pen
+  strokePen.setStyle( strokeStyle( state() ) );
+  painter->setPen( strokePen );
   painter->setBrush( QBrush( color, Qt::SolidPattern ) );
   painter->drawRect( rect );
   painter->setFont( font() );
@@ -291,6 +286,11 @@ QString QgsModelComponentGraphicItem::truncatedTextForItem( const QString &text
   return t;
 }
 
+Qt::PenStyle QgsModelComponentGraphicItem::strokeStyle( QgsModelComponentGraphicItem::State ) const
+{
+  return Qt::SolidLine;
+}
+
 QPicture QgsModelComponentGraphicItem::iconPicture() const
 {
   return QPicture();
@@ -558,6 +558,12 @@ QPicture QgsModelParameterGraphicItem::iconPicture() const
   return mPicture;
 }
 
+void QgsModelParameterGraphicItem::updateStoredComponentPosition( const QPointF &pos )
+{
+  if ( QgsProcessingModelParameter *param = dynamic_cast< QgsProcessingModelParameter * >( component() ) )
+    model()->parameterComponent( param->parameterName() ).setPosition( pos );
+}
+
 void QgsModelParameterGraphicItem::deleteComponent()
 {
   if ( const QgsProcessingModelParameter *param = dynamic_cast< const QgsProcessingModelParameter * >( component() ) )
@@ -733,6 +739,12 @@ QString QgsModelChildAlgorithmGraphicItem::linkPointText( Qt::Edge edge, int ind
   return QString();
 }
 
+void QgsModelChildAlgorithmGraphicItem::updateStoredComponentPosition( const QPointF &pos )
+{
+  if ( QgsProcessingModelChildAlgorithm *child = dynamic_cast< QgsProcessingModelChildAlgorithm * >( component() ) )
+    model()->childAlgorithm( child->childId() ).setPosition( pos );
+}
+
 void QgsModelChildAlgorithmGraphicItem::deleteComponent()
 {
   if ( const QgsProcessingModelChildAlgorithm *child = dynamic_cast< const QgsProcessingModelChildAlgorithm * >( component() ) )
@@ -830,6 +842,12 @@ QPicture QgsModelOutputGraphicItem::iconPicture() const
   return mPicture;
 }
 
+void QgsModelOutputGraphicItem::updateStoredComponentPosition( const QPointF &pos )
+{
+  if ( QgsProcessingModelOutput *output = dynamic_cast< QgsProcessingModelOutput * >( component() ) )
+    model()->childAlgorithm( output->childId() ).modelOutput( output->name() ).setPosition( pos );
+}
+
 void QgsModelOutputGraphicItem::deleteComponent()
 {
   if ( const QgsProcessingModelOutput *output = dynamic_cast< const QgsProcessingModelOutput * >( component() ) )
@@ -842,4 +860,115 @@ void QgsModelOutputGraphicItem::deleteComponent()
 }
 
 
+
+
+QgsModelCommentGraphicItem::QgsModelCommentGraphicItem( QgsProcessingModelComment *comment, QgsModelComponentGraphicItem *parentItem, QgsProcessingModelAlgorithm *model, QGraphicsItem *parent )
+  : QgsModelComponentGraphicItem( comment, model, parent )
+  , mParentComponent( parentItem->component()->clone() )
+  , mParentItem( parentItem )
+{
+  setLabel( comment->description() );
+
+  QFont f = font();
+  f.setPixelSize( 9 );
+  setFont( f );
+}
+
+void QgsModelCommentGraphicItem::contextMenuEvent( QGraphicsSceneContextMenuEvent *event )
+{
+  QMenu *popupmenu = new QMenu( event->widget() );
+  QAction *removeAction = popupmenu->addAction( QObject::tr( "Remove" ) );
+  connect( removeAction, &QAction::triggered, this, &QgsModelCommentGraphicItem::deleteComponent );
+  QAction *editAction = popupmenu->addAction( QObject::tr( "Edit" ) );
+  connect( editAction, &QAction::triggered, this, &QgsModelCommentGraphicItem::editComponent );
+  popupmenu->exec( event->screenPos() );
+}
+
+QgsModelCommentGraphicItem::~QgsModelCommentGraphicItem() = default;
+
+QColor QgsModelCommentGraphicItem::fillColor( QgsModelComponentGraphicItem::State state ) const
+{
+  QColor c( 230, 230, 230 );
+  switch ( state )
+  {
+    case Selected:
+      c = c.darker( 110 );
+      break;
+    case Hover:
+      c = c.darker( 105 );
+      break;
+
+    case Normal:
+      break;
+  }
+  return c;
+}
+
+QColor QgsModelCommentGraphicItem::strokeColor( QgsModelComponentGraphicItem::State state ) const
+{
+  switch ( state )
+  {
+    case Selected:
+      return QColor( 50, 50, 50 );
+    case Hover:
+    case Normal:
+      return QColor( 150, 150, 150 );
+  }
+  return QColor();
+}
+
+QColor QgsModelCommentGraphicItem::textColor( QgsModelComponentGraphicItem::State ) const
+{
+  return QColor( 100, 100, 100 );
+}
+
+Qt::PenStyle QgsModelCommentGraphicItem::strokeStyle( QgsModelComponentGraphicItem::State ) const
+{
+  return Qt::DotLine;
+}
+
+void QgsModelCommentGraphicItem::updateStoredComponentPosition( const QPointF &pos )
+{
+  if ( QgsProcessingModelComment *comment = modelComponent() )
+  {
+    comment->setPosition( pos );
+  }
+}
+
+void QgsModelCommentGraphicItem::deleteComponent()
+{
+  if ( QgsProcessingModelComment *comment = modelComponent() )
+  {
+    comment->setDescription( QString() );
+    emit changed();
+    emit requestModelRepaint();
+  }
+}
+
+void QgsModelCommentGraphicItem::editComponent()
+{
+  if ( mParentItem )
+  {
+    mParentItem->editComment();
+  }
+}
+
+QgsProcessingModelComment *QgsModelCommentGraphicItem::modelComponent()
+{
+  if ( const QgsProcessingModelChildAlgorithm *child = dynamic_cast< const QgsProcessingModelChildAlgorithm * >( mParentComponent.get() ) )
+  {
+    return model()->childAlgorithm( child->childId() ).comment();
+  }
+  else if ( const QgsProcessingModelParameter *param = dynamic_cast< const QgsProcessingModelParameter * >( mParentComponent.get() ) )
+  {
+    return model()->parameterComponent( param->parameterName() ).comment();
+  }
+  else if ( const QgsProcessingModelOutput *output = dynamic_cast< const QgsProcessingModelOutput * >( mParentComponent.get() ) )
+  {
+    return model()->childAlgorithm( output->childId() ).modelOutput( output->name() ).comment();
+  }
+  return nullptr;
+}
+
+
 ///@endcond
diff --git a/src/gui/processing/models/qgsmodelcomponentgraphicitem.h b/src/gui/processing/models/qgsmodelcomponentgraphicitem.h
index a6e5dfdadc6..ab75a3201a3 100644
--- a/src/gui/processing/models/qgsmodelcomponentgraphicitem.h
+++ b/src/gui/processing/models/qgsmodelcomponentgraphicitem.h
@@ -21,11 +21,13 @@
 #include <QGraphicsObject>
 #include <QFont>
 #include <QPicture>
+#include <QPointer>
 
 class QgsProcessingModelComponent;
 class QgsProcessingModelParameter;
 class QgsProcessingModelChildAlgorithm;
 class QgsProcessingModelOutput;
+class QgsProcessingModelComment;
 class QgsProcessingModelAlgorithm;
 class QgsModelDesignerFlatButtonGraphicItem;
 class QgsModelDesignerFoldButtonGraphicItem;
@@ -158,6 +160,13 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
      */
     QPointF calculateAutomaticLinkPoint( const QPointF &point, Qt::Edge &edge SIP_OUT ) const;
 
+    /**
+     * Called when the comment attached to the item should be edited.
+     *
+     * The default implementation does nothing.
+     */
+    virtual void editComment() {}
+
   signals:
 
     // TODO - rework this, should be triggered externally when the model actually changes!
@@ -222,6 +231,11 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
      */
     virtual QColor textColor( State state ) const = 0;
 
+    /**
+     * Returns the stroke style to use while rendering the outline of the item.
+     */
+    virtual Qt::PenStyle strokeStyle( State state ) const;
+
     /**
      * Returns a QPicture version of the item's icon, if available.
      */
@@ -232,6 +246,11 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
      */
     virtual QPixmap iconPixmap() const;
 
+    /**
+     * Updates the position stored in the model for the associated comment
+     */
+    virtual void updateStoredComponentPosition( const QPointF &pos ) = 0;
+
   private:
 
     void updateToolTip( const QPointF &pos );
@@ -292,6 +311,7 @@ class GUI_EXPORT QgsModelParameterGraphicItem : public QgsModelComponentGraphicI
     QColor strokeColor( State state ) const override;
     QColor textColor( State state ) const override;
     QPicture iconPicture() const override;
+    void updateStoredComponentPosition( const QPointF &pos ) override;
 
   protected slots:
 
@@ -337,6 +357,7 @@ class GUI_EXPORT QgsModelChildAlgorithmGraphicItem : public QgsModelComponentGra
 
     int linkPointCount( Qt::Edge edge ) const override;
     QString linkPointText( Qt::Edge edge, int index ) const override;
+    void updateStoredComponentPosition( const QPointF &pos ) override;
 
   protected slots:
 
@@ -382,6 +403,7 @@ class GUI_EXPORT QgsModelOutputGraphicItem : public QgsModelComponentGraphicItem
     QColor strokeColor( State state ) const override;
     QColor textColor( State state ) const override;
     QPicture iconPicture() const override;
+    void updateStoredComponentPosition( const QPointF &pos ) override;
 
   protected slots:
 
@@ -391,6 +413,57 @@ class GUI_EXPORT QgsModelOutputGraphicItem : public QgsModelComponentGraphicItem
 
     QPicture mPicture;
 };
+
+
+
+/**
+ * \ingroup gui
+ * \brief A graphic item representing a model comment in the model designer.
+ * \warning Not stable API
+ * \since QGIS 3.14
+ */
+class GUI_EXPORT QgsModelCommentGraphicItem : public QgsModelComponentGraphicItem
+{
+    Q_OBJECT
+
+  public:
+
+    /**
+     * Constructor for QgsModelCommentGraphicItem for the specified \a comment, with the specified \a parent item.
+     *
+     * The \a model argument specifies the associated processing model. Ownership of \a model is not transferred, and
+     * it must exist for the lifetime of this object.
+     *
+     * Ownership of \a output is transferred to the item.
+     */
+    QgsModelCommentGraphicItem( QgsProcessingModelComment *comment SIP_TRANSFER,
+                                QgsModelComponentGraphicItem *parentItem,
+                                QgsProcessingModelAlgorithm *model,
+                                QGraphicsItem *parent SIP_TRANSFERTHIS );
+    ~QgsModelCommentGraphicItem() override;
+    void contextMenuEvent( QGraphicsSceneContextMenuEvent *event ) override;
+
+  protected:
+
+    QColor fillColor( State state ) const override;
+    QColor strokeColor( State state ) const override;
+    QColor textColor( State state ) const override;
+    Qt::PenStyle strokeStyle( State state ) const override;
+    void updateStoredComponentPosition( const QPointF &pos ) override;
+
+  protected slots:
+
+    void deleteComponent() override;
+    void editComponent() override;
+  private:
+
+    QgsProcessingModelComment *modelComponent();
+
+    std::unique_ptr< QgsProcessingModelComponent > mParentComponent;
+    QPointer< QgsModelComponentGraphicItem > mParentItem;
+
+
+};
 ///@endcond
 
 #endif // QGSMODELCOMPONENTGRAPHICITEM_H
diff --git a/src/gui/processing/models/qgsmodelgraphicsscene.cpp b/src/gui/processing/models/qgsmodelgraphicsscene.cpp
index c4d72ee35d7..4e2e0263c67 100644
--- a/src/gui/processing/models/qgsmodelgraphicsscene.cpp
+++ b/src/gui/processing/models/qgsmodelgraphicsscene.cpp
@@ -58,6 +58,11 @@ QgsModelComponentGraphicItem *QgsModelGraphicsScene::createOutputGraphicItem( Qg
   return new QgsModelOutputGraphicItem( output, model, nullptr );
 }
 
+QgsModelComponentGraphicItem *QgsModelGraphicsScene::createCommentGraphicItem( QgsProcessingModelAlgorithm *model, QgsProcessingModelComment *comment, QgsModelComponentGraphicItem *parentItem ) const
+{
+  return new QgsModelCommentGraphicItem( comment, parentItem, model, nullptr );
+}
+
 void QgsModelGraphicsScene::createItems( QgsProcessingModelAlgorithm *model, QgsProcessingContext &context )
 {
   // model input parameters
@@ -70,6 +75,8 @@ void QgsModelGraphicsScene::createItems( QgsProcessingModelAlgorithm *model, Qgs
     mParameterItems.insert( it.value().parameterName(), item );
     connect( item, &QgsModelComponentGraphicItem::requestModelRepaint, this, &QgsModelGraphicsScene::rebuildRequired );
     connect( item, &QgsModelComponentGraphicItem::changed, this, &QgsModelGraphicsScene::componentChanged );
+
+    addCommentItemForComponent( model, it.value(), item );
   }
 
   // input dependency arrows
@@ -98,6 +105,8 @@ void QgsModelGraphicsScene::createItems( QgsProcessingModelAlgorithm *model, Qgs
     mChildAlgorithmItems.insert( it.value().childId(), item );
     connect( item, &QgsModelComponentGraphicItem::requestModelRepaint, this, &QgsModelGraphicsScene::rebuildRequired );
     connect( item, &QgsModelComponentGraphicItem::changed, this, &QgsModelGraphicsScene::componentChanged );
+
+    addCommentItemForComponent( model, it.value(), item );
   }
 
   // arrows linking child algorithms
@@ -148,6 +157,8 @@ void QgsModelGraphicsScene::createItems( QgsProcessingModelAlgorithm *model, Qgs
       connect( item, &QgsModelComponentGraphicItem::requestModelRepaint, this, &QgsModelGraphicsScene::rebuildRequired );
       connect( item, &QgsModelComponentGraphicItem::changed, this, &QgsModelGraphicsScene::componentChanged );
 
+      addCommentItemForComponent( model, outputIt.value(), item );
+
       QPointF pos = outputIt.value().position();
 
       // find the actual index of the linked output from the child algorithm it comes from
@@ -164,12 +175,7 @@ void QgsModelGraphicsScene::createItems( QgsProcessingModelAlgorithm *model, Qgs
         i++;
       }
 
-#if 0
-    if pos is None:
-      pos = ( alg.position() + QPointF( alg.size().width(), 0 )
-              + self.algItems[alg.childId()].linkPoint( Qt.BottomEdge, idx ) )
-#endif
-              item->setPos( pos );
+      item->setPos( pos );
       outputItems.insert( outputIt.key(), item );
       addItem( new QgsModelArrowItem( mChildAlgorithmItems[it.value().childId()], Qt::BottomEdge, idx, item ) );
     }
@@ -249,5 +255,21 @@ QList<QgsModelGraphicsScene::LinkSource> QgsModelGraphicsScene::linkSourcesForPa
   return res;
 }
 
+void QgsModelGraphicsScene::addCommentItemForComponent( QgsProcessingModelAlgorithm *model, const QgsProcessingModelComponent &component, QgsModelComponentGraphicItem *parentItem )
+{
+  if ( !component.comment() || component.comment()->description().isEmpty() )
+    return;
+
+  QgsModelComponentGraphicItem *commentItem = createCommentGraphicItem( model, component.comment()->clone(), parentItem );
+  commentItem->setPos( component.comment()->position().x(), component.comment()->position().y() );
+  addItem( commentItem );
+  connect( commentItem, &QgsModelComponentGraphicItem::requestModelRepaint, this, &QgsModelGraphicsScene::rebuildRequired );
+  connect( commentItem, &QgsModelComponentGraphicItem::changed, this, &QgsModelGraphicsScene::componentChanged );
+
+  std::unique_ptr< QgsModelArrowItem > arrow = qgis::make_unique< QgsModelArrowItem >( parentItem, commentItem );
+  arrow->setPenStyle( Qt::DotLine );
+  addItem( arrow.release() );
+}
+
 ///@endcond
 
diff --git a/src/gui/processing/models/qgsmodelgraphicsscene.h b/src/gui/processing/models/qgsmodelgraphicsscene.h
index 5830db8ca2c..b35a25d5376 100644
--- a/src/gui/processing/models/qgsmodelgraphicsscene.h
+++ b/src/gui/processing/models/qgsmodelgraphicsscene.h
@@ -26,6 +26,8 @@ class QgsModelComponentGraphicItem;
 class QgsProcessingModelParameter;
 class QgsProcessingModelChildAlgorithm;
 class QgsProcessingModelOutput;
+class QgsProcessingModelComponent;
+class QgsProcessingModelComment;
 
 ///@cond NOT_STABLE
 
@@ -118,6 +120,13 @@ class GUI_EXPORT QgsModelGraphicsScene : public QGraphicsScene
      */
     virtual QgsModelComponentGraphicItem *createOutputGraphicItem( QgsProcessingModelAlgorithm *model, QgsProcessingModelOutput *output ) const SIP_FACTORY;
 
+    /**
+     * Creates a new graphic item for a model comment.
+     */
+    virtual QgsModelComponentGraphicItem *createCommentGraphicItem( QgsProcessingModelAlgorithm *model, QgsProcessingModelComment *comment,
+        QgsModelComponentGraphicItem *parentItem ) const SIP_FACTORY;
+
+
   private:
 
     struct LinkSource
@@ -128,6 +137,8 @@ class GUI_EXPORT QgsModelGraphicsScene : public QGraphicsScene
     };
     QList< LinkSource > linkSourcesForParameterValue( QgsProcessingModelAlgorithm *model, const QVariant &value, const QString &childId, QgsProcessingContext &context ) const;
 
+    void addCommentItemForComponent( QgsProcessingModelAlgorithm *model, const QgsProcessingModelComponent &component, QgsModelComponentGraphicItem *parentItem );
+
     Flags mFlags = nullptr;
 
     QMap< QString, QgsModelComponentGraphicItem * > mParameterItems;