in 2020, you should be able to go to a login page for office 365 and have a drop down menu or listing of all your O365 accounts. You should be able to quickly choose which account you want open in a browser and have multiple accounts open at once. You should also be able to toggle back and forth between multiple accounts within each app. I have several O365 accounts:

personal, school, work, client-guest and client accounts. This is ridiculous that I struggle to find documents and revisions across so many one drive accounts