This tool, which is available from the new F12 "dev tools" panel,
is a native port of @rduivenvoorde's network logger plugin.
It shows a list of ongoing and completed network requests, along
with a whole load of useful detail like request and reply status,
headers, errors, SSL configuration errors, timeouts, cache status,
etc.
Also has loads of polish and useful capabilities, such as the ability
to filter requests by URL substrings and status, and you can right-click
requests to open the URL in a browser or copy them as a cURL command.