Indie game storeFree gamesFun gamesHorror games
Game developmentAssetsComics

I couldn’t find any resources on how game maker even made those IDs to make my own.

Should you need this in the future, any GUID will do. In GMEdit, I just use random characters (without respecting the format) and it works.

Later versions (2.3 and newer) mostly eliminate GUIDs (except in sprites).