This is working today in the web client on Edge & Chrome. The team is actively investigating feasibility in the desktop client.
We are working on the release of the Tasks application in Microsoft Teams that will aggregate data from Microsoft To-Do, Planner and Outlook with more capabilities on the way. You can see Planner data in Kanban views today, and the Tasks app will continue to support that view. In January we announced task publishing which will release with the new app. Get an overview at https://youtu.be/rTATVGroEsQ.
Thank you for your continued feedback! We are excited to announce we are currently testing this feature internally. We will share an update as soon as it is available.
The ability to use multiple Teams accounts at the same time is supported on iOS & Android today. The feature team is continuing to work on support for multiple accounts on desktop and web clients. We’ll keep you posted as we have more details.