We’re currently working on defining a compact mode experience. I will post more details when we have more to share.
It seems to me that the "compact mode" for Teams has been in development and without any ETA now for years. The current desktop client is dreadful in respect to pure chat. It clearly is attempting to force users to utilize Teams as a "platform service", which "can" be nice if you're into clicking around all day, logging into dozens of fancy apps because every colleague uses different applications for their task management or whatever. I was really excited when my company first started using Teams.. by now it's become more of a bother than an effective tool to get anything done.
A simple chat client pop-out would at least make communication better, but I suppose that's not the intent.