Mailbox in Monterey on Mac

Thanks, Mal-S!

I tried your instructions in Mail Preferences, then quit Mail and then *relaunched Mail. However, still no Junk mailbox in sidebar. (Also, I actually want to have an ALL JUNK mailbox, in my Favorites sidebar, just like there is an ALL TRASH mailbox in my Favorites already, since I have several email accounts that I access through Mac Mail.)

*Maybe you meant I should shut down and RELAUNCH my Mac, the open Mail app?

Mal-S:

I think that did it: I pointed on the top of the sidebar above Favorites, which reveals a plus inside a circle. A dialog box appeared with a popup menu to select a mailbox, one of which was ALL JUNK. I chose it and I now have an ALL JUNK folder once again. I'd like to test it out, but for once I have not received any junk mail today! I'm sure I will before the day is done! ;-)

Thanks so much for your help!