There are a couple of other special pages where the new entity selector control can be used to select groups:
- ExportTranslationsSpecialPage (https://meta.wikimedia.org/wiki/Special:ExportTranslations)
- AggregateGroupsSpecialPage (https://meta.wikimedia.org/wiki/Special:AggregateGroups - you should have translation admin rights)
The new entity selector was added in T298960: Create the message group/prefix selector component and can be seen in action in https://meta.wikimedia.org/wiki/Special:MessageGroupStats. Try typing "Main" in the textbox and you should see some suggestions appear. The entity selector allows users to select message groups.
This patch added the entity selector to Special:MessageGroupStats page. See code in file: resources/src/ext.translate.special.languagestats/index.js. The patch also contains the actual code for the entity selector which will not be needed when adding the entity selector to other pages.