Using Classic Outlook on Windows for personal email, calendar, and contact management
Finally this is working! I have been able to add inboxes/subfolders to favourites from shared mailboxes.
It's pretty basic but at least the folders are pinned and there is an indicator for the number of unread emails.
This feature could be enhanced by enabling client-side nicknames and colour coding for the pinned folders.
Generally, very happy this feature has been added - it was a loooong wait.