Hello,

A few weeks ago, I posted on this ML a proof of concept about dynamic
numbering of headlines in an Org buffer. Since then, I worked on it more
seriously, improved it, and threw in some features. Here is an excerpt
of its commentary section:

    This library provides dynamic numbering for Org headlines.  Use
   
        <M-x org-num-mode>
   
    to toggle it.
   
    You can select what is numbered according to level, tags, COMMENT
    keyword, or UNNUMBERED property.  You can also skip footnotes
    sections.  See `org-num-max-level', `org-num-skip-tags',
    `org-num-skip-commented', `org-num-skip-unnumbered', and
    `org-skip-footnotes' for details.
   
    You can also control how the numbering is displayed by setting
   `org-num-face' and `org-num-format-function'.

I tested it a bit, even in relatively large documents like the Org
manual, without problem. I also wrote a test suite for that library.

Since it is very much Org-specific, and a basic feature you could expect
from Org, I'd like to add it in core. So, if there is no strong
objection to it, it can go in Org 9.3.

I attach the library for further testing, suggestions, remarks… Let me
know what you think.

Regards,

-- 
Nicolas Goaziou