r.patch
Creates a composite raster layer by using one (or more) layer(s) to fill in areas of "no data" in another map layer.
Raster (r.*)
QgsProcessingParameterMultipleLayers|input|Raster layers to be patched together|3|None|False
QgsProcessingParameterBoolean|-z|Use zero (0) for transparency instead of NULL|False
QgsProcessingParameterRasterDestination|output|Patched