Using New Outlook on Windows for personal email, calendar, and contact management
This works OK and is definitely better than nothing - although still not as useful as a consolidated inbox (in my opinion).
However, make sure you highlight each inbox (or any other folder) you want to add to your Favorites by right clicking on the inbox/folder BEFORE you click on the folder's "..." menu. If you don't select the new inbox/folder first, i.e., if you just go straight to the "..." menu of the new folder you want to add, the previous folder (whatever it was) remains highlighted; and selecting "add to favorites" on the new folder "..." menu will add a folder you didn't expect or will add the previous inbox/folder again. Go figure.
I discovered this the hard way :-)