[luatex] How to correct expand user commands in lualatex?

[Alexandr Kozlovskiy]

Hello Henri. I not use your solution,because I need in fully tagged 
formula,i mean struct elem with actualtext,which have reference in mc 
element,which have a formula. Tagpdf package allow to solve this 
problem. Also it not solved problem in your code,when formula start in 
one page,and finished on other page,but the main reason it first.

As for expanding of command,it's become very strange situation. If i not 
use \expanded,it works ok,but only if i haven't space after end of 
equation (see 
https://tex.stackexchange.com/questions/524927/how-to-correct-expand-commands-to-insert-it-in-actualtext?noredirect=1#comment1329070_524927). 
So there is no way to solve my problem,using latex way,and i should 
develop external scripts,which expand users commands,or it exists way to 
solve my problem,because without \expanded command and without space all 
works as expected.