Right now we are looking into an archiving function / improving the current archive functionality. Users will be able to move group chats and 1-on-1 chats to an archive and also look into the archive itself. That way you can keep your chat sidebar clean.
Would that solve your requirements?
As Sven already stated we started with creating concept and visuals. However, development of this improvement has not started yet but is still planned.
This feature is still planned, but currently not in development. We will update this request as soon as development starts