Feature summary: I would like a way to select all sites in the wiki farm (everything connected in CentralAuth) in Special:GlobalWatchlistSettings.

Use case(s): It would save time for users who are active on many wikis, so that they do not need to manually add all of the wikis they want.

Notes: This might need to wait until T268261: Add a list or autocompletion for sites on Special:GlobalWatchlistSettings is done.