scratchなどで書いた走り書きをリージョン選択してhowmバッファを作成。最後の行が":"で始まってると、それをタイトルにする。

region2howm.el

;;; region2howm.el --- copy a region to howm buffer.

;; Copyright (C) 2013  serian

;; Author: serian <serian>
;; Keywords: tools

;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:
;; Create howm buffer with a region.
;; If the end line of the region starts with ":", this line is copied as title without ":".
;;
;;; Code:
(require 'howm)
(defvar region2howm-title-mark ":")
(defun region2howm-get-region (start end)
  (interactive "r")
  (save-excursion
    (let* ((title (region2howm-get-title end))
    (end-tmp (if (not (string= title "")) (progn (previous-line) (end-of-line) (point)) end))
	  (buf (buffer-substring-no-properties start end-tmp)))
      (howm-create-file-with-title title nil nil nil buf))))

(defun region2howm-get-title (end)
    (goto-char end)
    (when (bolp) (previous-line))
    (beginning-of-line)
    (if (region2howm-get-title-p (point))
	(progn
	  (right-char)
	  (let ((pos1 (point)))
	    (end-of-line)
	    (let ((pos2 (point)))
	      (buffer-substring-no-properties pos1 pos2)))) ""))

(defun region2howm-get-title-p (pt)
  (if (string= (char-to-string (char-after pt)) region2howm-title-mark) t nil))

(provide 'region2howm)
;;; region2howm.el ends here