Consider that dirlist-format %r only considers directly descendants, while a maildir can have multiple levels of subdirectories.
It would be useful to get a number for the unreads anywhere under a directory.
While we're at it, it would be great to have "unread" seperately; for small screens it makes a huge difference in screen real estate.
I work with a lot of folders. So far I haven't found a terminal flow that beats webmail or desktop. I think this feature, together with the important https://todo.sr.ht/~sircmpwn/aerc2/228, are the two missing pieces to bring aerc there.
So my proposal:
%e: recent messages %E: recent messages (recursive) %u: unseen messages %U: unseen messages (recursive) %c: total message count %C: total message count (recursive)