We know you are patiently waiting for this feature. This feature is being implemented in stages. Fast tenant switching is currently in testing both internally and with early customers. We expect to release to the public in the Fall. I’ll post an update once it’s rolling out.
Full multi-tenant, multi-user support will be added after fast tenant switching.
~AlexJim Scheirer commented
Temporary Fix: Use InPrivate (edge), Private (Firefox) or Incognito (chrome) and you can log into each o365 account without conflicting with the other browser windows. So you can be logged into all 4 at the same time and not have a problem. we do this when we test with multiple user account in the same tenant as well as multiple accounts across multiple tenamnts