Werner, I'm facing the same problem, but without ever having used the sidebar. For switching mailing list folders I'm typing <c><?>. Then I can select from a list of mailing list folders. With the previous mutt version from Leap 42.2 I saw the number of new messages in front of each folder. Now I only see a 'N' if there are new messages. No idea how to reconfigure that. :-( Any ideas?