This feature request is still working its way through the backlog queue.
We are working on a better experience in Teams when a user is not connected to the internet. No timeline to share at this point, but we will keep you posted.
We are working on a design with more density in mind. Until this design is solidified we are putting this item back to Under Review.
Multi-window chat is in testing. I hope to have great news regarding rollout to the public rings soon.
We are working to ensure that multi-window and other future multi-window experiences are of the highest quality when they release.