Well, it comes up every now and again, but the fact you have to either play the custom game mode or update the files each time there is a new GD patch as well as figure out how to do any of that in the first place probably scares people off.
I will look into it when I get around to redoing my modding tools, but that is going to be a while.
Can someone guide me how to generate rainbow files from mods (like Grim League, Diablo 3, etc.)?
When there is a new Playtest patch and you are not using the program to generate the files yourself you will have to check the repo for an update. The files on the repo will have the playtest number in the version tooltip on the ingame filter button, to keep track of it more easily, new files should be available within 12 hours of the new version becoming available on Steam. If you’re generating the files yourself, it won’t update the version tooltip. Keep in mind you cannot generate the files yourself if the tool is saying it is using internal files (a workaround for errors), as those have not been updated.
The repo on GitHub for downloads.
Obligatory + Broken Record - Note: Yes, the new tools are still being made 
Awesome to see you updating it for even us in the playtest. You are a legend!