Additional features, settings, or issues not covered by specific Microsoft Teams categories
I am a little late to this thread but it took me a minute to figure it out, so I am adding an answer.
*I did NOT find a way to Favorite the Team, but I did find a way to Favorite a channel under the team. So if you only have 1 channel....it is usually called General.
- Select the three dots (...) next to channel name (ie: General).
- Select SHOW IN
- Select FAVORITES
If you do not see that, you may need to create the section, so click "New Section" & title it Favorites.