Mu4e: mark as read and move to spam folder action.

.emacs.el

(setq mu4e-spam-folder "/thalheim.io/Spam")

;; Mark as read and move to spam
(add-to-list 'mu4e-marks
             '(spam
               :char       "S"
               :prompt     "Spam"
               :show-target (lambda (target) mu4e-spam-folder)
               :action      (lambda (docid msg target)
                              (mu4e~proc-move docid mu4e-spam-folder "+S-u-N"))))

(mu4e~headers-defun-mark-for spam)
(define-key mu4e-headers-mode-map (kbd "S") 'mu4e-headers-mark-for-spam)