I use 1.20.1 mc and copycats 1.2.6
If put glowstone in copycats block and reenter the world the block doesn't glow.

There is written, that I have to edit file inside create mod. Do you know how?

Duplicate of #52. Also an issue in creates copycat class which we extend

You should leave this to the Create devs. That comment is just a workaround in the source code and editing source code is quite complex.