A manual way to do this is to enter "isflagged:yes" or "isread:no" in the the search field. Be sure to select Inbox to the left of the search field (or any other folder, you wish to search) or you will also see flagged/unread messages in trash, drafts, etc. Maybe this can be automated - I tried to look at Quick steps, but couldn't see how to enter search queries there. I found it by trial and error - cannot find good documentation on this or other flags in the Outlook help. You can enter extra text to search the flagged or unread messages for. Flags can also be combined, but I don't have a good list of flags.