Toggling off the "Keep separate item group" mod setting will crash the game on load with the following error:

https://i.imgur.com/S19YgAE.png

I had a lot of mods running but even disabling every single one of them (except this mod's dependency) will still cause the crash. I'm surprised no one mentioned this. Running Factorio 1.1.69 which is the current latest version available.

Should be fixed in 0.0.5. Please check it.
I'm also surprised that no one wrote about this bug, it is really easy to trigger.

It is working perfectly fine now, thank you!