I wanted to e-mail all the EmacsConf speakers who had already uploaded their videos, and I wanted to keep track of the fact that I'd mailed them by adding a note to the :LOGBOOK: drawer in their talk heading. That way, organizers can just look at the logbook to see if we've mailed someone instead of digging through our mailboxes.

org-store-log-note assumes that it's called from the log buffer created by org-add-log-note. It doesn't seem to have a smaller function that can be called to store notes non-interactively, but that's okay. We can just set up the correct markers and call it from a temporary buffer.

(defun emacsconf-add-to-logbook (note)
  "Add NOTE as a logbook entry for the current subtree."
  (move-marker org-log-note-return-to (point))
  (move-marker org-log-note-marker (point))
  (with-temp-buffer
    (insert note)
    (let ((org-log-note-purpose 'note))
      (org-store-log-note))))

Then it's convenient to have a function that adds a note to a specified talk:

(defun emacsconf-add-to-talk-logbook (talk note)
  "Add NOTE as a logbook entry for TALK."
  (interactive (list (emacsconf-complete-talk) (read-string "Note: ")))
  (save-excursion
    (emacsconf-with-talk-heading talk
      (emacsconf-add-to-logbook note))))

I discard many drafts on the way to finalizing the process, so I want the note to be stored only after I actually send the mail. That's the job of message-sent-hook. My mail merge function calls compose-mail, sets up the body of the buffer, and then adds a lambda function to message-sent-hook to file the note in the logbook when sent.

(add-hook 'message-sent-hook
          `(lambda ()
             (mapc
              (lambda (o)
                (emacsconf-add-to-talk-logbook o "Sent speaker-after-video email"))
              (list ,@(mapcar (lambda (talk) (plist-get talk :slug)) talks))))
          nil t)

To see the mail merge code in context, you can check out the TODO entry at https://emacsconf.org/2022/organizers-notebook/#speaker-after-video . It uses functions from emacsconf.el and emacsconf-mail.el at https://git.emacsconf.org/emacsconf-el/ .