I believe @turt2live's feedback on making matrix-org/matrix-react-sdk#2575 more usable for actual custom tag powerusers is:

• Show all rooms by default in the RoomList
• As you select custom tags, they "pull rooms" out of the overall roomlist in order to file them in a dedicated section for that tag. The rest of the list is still present.
  • (or should we filter the whole list to just be that tag?)