We’re currently working on defining a compact mode experience. I will post more details when we have more to share.
"As we look to 2019, we will be pursuing plans to continue to make the product more and more space efficient. We see this as a guiding design principle, as well as a backlog of requests from UserVoice that we catalogue, discuss, debate, brainstorm and problem solve."
The very first reaction I had to the migration from Skype to MS Teams was "how do I reduce the amount of unnecessary whitespace"
This is a basic necessity for any sort competitive, modern application, and it appears like this has not been made a priority, judging by the sheer amount of conversation and the complete lack of this option in the latest version of MSTeams.