New release v1.12.9, with a number of fixes, doc improvements
and some new features:

• new command mu4e-analyze-last-query which shows information about
  how the server interpreted the last query; this can be useful if you
  don't get the result you expected.

• When you ask for bookmarks or maildirs through mu4e-search-bookmark or
  mu4e-search-maildir, unread counts are displayed in the (default)
  completions UI next to the maildir or bookmark. If you don't want to
  see these counts, set mu4e-hide-short-counts to non-nil.

• experimental: a "transient" menu, which provides easy access to some
  common (and some not so common) functions in mu4e. For now, you can
  enable this with:

      (require 'mu4e-transient)
      (global-set-key (kbd "C-c m") #'mu4e-transient-menu)

This requires you to have the "transient" package, which means Emacs
28 or later or alternatively you can install it manually. As stated,
it's experimental and will be change / expanded over time, but already
I find it quite useful.

• gnus mailing-list management commands such as
  gnus-mailing-list-subscribe, gnus-mailing-list-unsubscribe now also
  work in mu4e. Also available through the transient menu.

• The mu server uses PCRE-compatible regexps (for addresses), which are
  not necessarily compatible with Emacs regular expressions. However,
  mu4e can now automatically translate; this depends on the pcre2el
  package which the user should install when using regular
  expression-addresses.

• the cleanup phase after indexing has been sped up significantly

• updated documentation; man-pages and mu4e reference manual