From an mu4e view, without prompt, save all attachments to a directory and open dired.

attach.el

(defvar bulk-saved-attachments-dir (expand-file-name "~/Documents/Attachments"))

(defun cleanse-subject (sub)
  (replace-regexp-in-string
   "[^A-Z0-9]+"
   "-"
   (downcase sub)))

(defun view-attachments-dired (&optional msg)
  "Saves all of the attachments in `msg' to a directory under
`bulk-saved-attachments-dir' which is derived from the subject
beloning to `msg'. Existing filenames will be overwritten without
prompt. The directories are not cleaned up in any way."
  (interactive)
  (let* ((msg (or msg (mu4e-message-at-point)))
         (id (cleanse-subject (mu4e-message-field msg :subject)))
         (attachdir (concat bulk-saved-attachments-dir "/" id))
         (count (hash-table-count mu4e~view-attach-map)))
    (if (> count 0)
        (progn
          (mkdir attachdir t)
          (dolist (num (number-sequence 1 count))
            (let* ((att (mu4e~view-get-attach msg num))
                   (fname (plist-get att :name))
                   (index (plist-get att :index))
                   fpath)
              (setq fpath (concat attachdir "/" fname))
              (mu4e~proc-extract
               'save (mu4e-message-field msg :docid)
               index mu4e-decryption-policy fpath)))
          (dired attachdir)
          (revert-buffer))
      (message "Nothing to extract."))))

(add-to-list 'mu4e-view-attachment-actions '("DDired" . view-attachments-dired) t)