you can switch in the settings area, it is faster then sign out and sign in, but the result is the same. You current can only be in one teams tenant at a time at the moment.
Work around: use teams desktop app for one tenant and for the others browser windows. Use a incognito window in your browser (the one that does not store logins, cookies, etc.) and go to office.com -> teams
The fun starts when you get called in parallel :)