Set org-num-max-level in .org file

Is it possible to set a specific value for org-num-max-level in each org-mode file like with #+OPTIONS: or #+startup ? Thanks.

Where is that variable defined? It is not bound at runtime on my system (Org 9.5.2).

org-num minor mode has to be activated for me to be able to access this variable

You cannot do it with #+startup or #+options, but you can set file-local variable via M-x make-local-variable