gerard.vermeulen@posteo.net writes:

> Attached you'll find a new patch trying to implement your suggestions.
> Interactive splitting by demarcation seems to work quite well (see the
> before and after splitting snippets in the PS).

Thanks!

> However, I cannot run the test because org-babel-demarcate-block
> always errors "org-element--cache: Emergency exit" while the same
> input works interactively. Could there be a problem of cache
> synchronization or something like that? Is there something I can do?

This was a bug in `org-element-copy'. Fixed, on main now.
https://git.savannah.gnu.org/cgit/emacs/org-mode.git/commit/?id=dfeff03c5

> I also did not yet look into how to propagate a switch like -n10.

-n10 is not a valid switch, AFAIK. We demand space: -n 10.
See 12.6 Literal Examples section of the manual.

I made some adjustments to the patch, making use of org-element API.
See the attached updated version of the patch.

I am not yet merging it as I found some weirdness with indentation.
Consider the following (indentation is important):

            #+BEGIN_SRC emacs-lisp -n 20
              ;; This exports with line number 20.
<point>       (message "This is line 21")
            #+END_SRC

After M-x org-babel-demarcate-block, I am getting

            #+BEGIN_SRC emacs-lisp -n 20
              ;; This exports with line number 20.
              #+END_SRC
              
#+begin_src emacs-lisp -n 20
  (message "This is line 21")
#+end_src