While some of the format specifiers for the local file browser clearly
don't make sense in the IMAP borser (such as user and group IDs), the
new mail indication seems to make very good sense; and in fact, mutt
already has the information required (it tells me what boxes have new
mail with the '.' command).  So can that be added to the IMAP browser
format, please?  Better yet, can the IMAP browser format be made
configurable like the local browser, possibly with a different set of %
expansions?  (But a set including %N, of course).

Unfortunately, the IMAP support in mutt still feels like 2nd class
citizenship :-(