Simple way to add parent node

Question

Is there a simple way to add parent node in org-mode?

* heading
... # 100 or more first-level headings over here
* heading # interspersed with ones with subtrees
** heading
** heading
*** heading
...

I would like to add a NEW HEADING to the above so that everything else shifts down and right.

* NEW HEADING
** heading
*** heading
*** heading
**** heading
...

Currently, selecting everything and hitting M-→ works just some of the time. It gets cumbersome when many sub and/or sub-sub headings are involved.

---

Note:

I presently use mark set to select region to be demoted. It works only in a specific way and not all the time. Namely, I need to:

1. C-@ ↓ somewhere above the first * heading
2. Move the cursor to the left-most * just below the region the be selected
3. Hit M-→

Any other method would fail incessantly.

Answer 1

This function inserts a new parent/root node above the current subtree and demotes the original subtree respectively:

(defun org-insert-parent-node ()
  (interactive)
  (catch 'exit
    (while (or (org-up-heading-safe)
               (= (org-outline-level) 1))
      (when (= (org-outline-level) 1)
        (org-insert-heading)
        (save-excursion
          (outline-next-heading)
          (org-demote)
          (throw 'exit t))))))

Edit: I reread your question and I think you also want to include first-level headings above the current subtree. With this command you can select the current subtree and any number of first-level headings above it:

(defun org-insert-parent-node (beg end)
  (interactive (list (region-beginning) (region-end)))
  (save-restriction
    (narrow-to-region beg end)
    (let ((beg (save-excursion
                 (goto-char beg)
                 (skip-chars-forward "* ")
                 (point)))
           (end (save-excursion
                  (goto-char end)
                  (line-beginning-position))))
       (goto-char beg)
       (org-insert-heading)
       (goto-char beg)
       (save-excursion
         (while (outline-next-heading)
           (unless (= end (point))
             (org-demote)))))))

Answer 2

org-demote-subtree does that. It is bound to C-c C->.

Answer 3

As you might know, org-mode files are plaintext-based and heading depth is determined by the number of * characters in front of it

This means you can simply insert a * in front of all headings you want to be demoted in plaintext instead of relying on org-mode functions. You don't even need to exit org-mode for that.

The easiest way to do this I know of is to enter rectangle-mark-mode (C-x SPC) at the beginning of the first line, navigate to the beginning of the last line and use string-insert-rectangle (C-t) to enter as many * as levels you want to demote the headings by.
(Evil-mode users can use C-v and I instead.)

EDIT: This only works if there is no text under headings

The slightly more complicated way that also works with text under heading is to mark the lines you want to demote and use replace-regexp to replace ^* with ** and ^SPC with SPCSPC.
(Evil-mode user can use C-V to mark and :'<,'>s/^*/**/g to replace)