@Aidan_Gibson Welcome to the forum. Please familiarize yourself with our Community Guidelines.
I moved your comment from the thread Base domain versus host: best of both worlds , because it didn’t fit there (that user wanted Bitwarden to create a sorted list of all services for which he had accounts in a given web domain). What you are asking for is more akin to what was requested in this thread.
I suggest that you read through all of the posts above. If you still believe that there is a way to implement what you are asking for that would not simply be equivalent to using Base Domain matching for all items, please provide a detailed explanation or example.