This feature item is still in the works. We will keep you posted as we have new info from the feature team.
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.
Should be able to have a channel or chat open in one window and an application tab (eg. OneNote or Planner) open in a separate window.
We have been iterating on different designs and are starting to test internally. I don’t have a timeframe but will keep you posted.Ian commented
Maybe a big floating + sign button to start a new conversation, with the actual new conversation field hidden until that button is pressed.