After an idea of [[:fr:User:Padawane]]¹ it would be great to add a drop-down list for the tags in Special:Recentchanges and Special:Newpages instead of an edit box. This would help users who don't know what are exactly the tags and users who use intensively the tags.
[[:fr:User:Dr Brains]] proposes to add two system messages to give the ability to the sysops of customizing the tags useful for Newpages and Recentchanges, possibly like the one in Special:Block.
The RecentChanges part of this is done in T161650: Replace "Tag filter" input with a dropdown+lookup widget in RCFilters.
T23383: Suggest tags for tag filter at Special:Contributions, Special:NewPages, Special:RecentChanges, and Special:Log