Using New Outlook on Windows for personal email, calendar, and contact management
I found this thread trying to find a way to see all email from all accounts in one inbox like we can in the mobile app, which I still don't see how to do in New Outlook on Windows 11. But to answer the original poster's question, you can add each inbox to your Favorites (and rename them so they're not all called "Inbox" in your favorites list). You'll then see which ones have new mail, and you can click on them to be in that inbox.