Not exactly Bug 51774, but:
while descriptions of what a parameter is supposed to mean/do are provided in the list of available parameters inside the template inspector, this is not (no longer?) true for required and already selected parameters. The only way to read their description is to remove them from the left panel and get them back in the list, where they can be selected again, but clearly this is not optimal. Not sure a tooltip would be the way, so I'm filing this separately.

Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=51774