It is possible to attach files to mu4e messages using dired (See (emacs)Dired), using the following steps (based on a post on the mu-discuss mailing list by Stephen Eglen).
To prepare for this, you need a special version of the
function so it understands mu4e buffers as well; so put in your configuration:
(require 'gnus-dired) ;; make the `gnus-dired-mail-buffers' function also work on ;; message-mode derived modes, such as mu4e-compose-mode (defun gnus-dired-mail-buffers () "Return a list of active message buffers." (let (buffers) (save-current-buffer (dolist (buffer (buffer-list t)) (set-buffer buffer) (when (and (derived-mode-p 'message-mode) (null message-sent-message-via)) (push (buffer-name buffer) buffers)))) (nreverse buffers))) (setq gnus-dired-mail-mode 'mu4e-user-agent) (add-hook 'dired-mode-hook 'turn-on-gnus-dired-mode)
Then, mark the file(s) in dired you would like to attach and press C-c RET C-a, and you’ll be asked whether to attach them to an existing message, or create a new one.