Support Low Priority Rooms
Matrix has support for tagging rooms. One of these tags is m.lowpriority
which indicates "These should be shown with lower precedence than others".
https://spec.matrix.org/legacy/client_server/r0.4.0.html#id154
This feature is very useful when you join lots of rooms for things like open source projects or support but don't want to always have them clogging up the list that you more frequently participate in (like group chats or specific projects that you are involved with) even if those chats have less activity than the large number of "low priority" chats.
Proposed Mockups:
I would take a look at what Element does. They have a section for low-priority rooms that is below the "regular" rooms.
Here you can see that "Favourites" are always on top, then "People" and "Rooms" for regular priority chats. These are the ones that I most frequently participate in. Then there is "Low Priority" at the bottom.