The Steam release seems to have wider support from the developers for creating new mods. The GoG release only has parts of this (like preincluded UnityModManager). For example, the modification template for modding the "Owlcat" way is missing.

I was able to find a github repo, but it is quite outdated (last update on 27th of March) and does not seem to work correctly. Is there any plan to add this to the GoG release as well? Or is there a way to get the up-to-date version of the template somewhere?