Have a "Recent" tab alongside "Favourites" in the Teams/Channel list
The favourites list of Teams/Channels is manually curated and can get big, quickly. Often, though you are moving between a small number of channels. Having a "Recent" section at the top that dynamically showed the 5 or so most used channels would be really useful
Scott White commented
Include, new chats, chat comments, channels, channel comments, uploads, calendar events, etc. Teams should not make me look for new activity. The more contacts and channels I become involved, or the more activity going on the less useful Teams becomes. Teams could do better highlighting activity, but instead the interface often displays data mostly inert data. I'm forced to dig a bit to see any activity. For example in chats I see all my contacts and one chat. But I may have 20 or more active chats. I don't need to see the status of all my contacts.