Using Classic Outlook on Windows for personal email, calendar, and contact management
Possible bandaid?
Create a subfolder in the main email account you use, start it with AA-"name" so that it appears at the top of the folder list in favorites.
Then go to the email account you want emails forwarded from, set up a rule that all emails get forwarded to the main account. Then in the main account set up a rule that all emails from the other account get moved to this new subfolder you created.
You can move the subfolders up into Favorites this way and make it "look" like another inbox folder.
Hope this makes sense, because it's working for me. You don't have full functionality of the account but at least you can monitor all new emails from multiple accounts this way