I want to disable the cosmetic slots, but I don´t know how

There is a smaller box next to every cosmetic slot if I'm not mistaken, however certain boxes toggle wrong items or do not respond in any way.

Sorry for getting to this this late. While the cosmetic slots are technically added by this mod, they're actually a feature of the Curios API. I haven't tested this myself, but you should be able to disable them in the curios config, more information here under "Creating a New Slot Type": https://github.com/TheIllusiveC4/Curios/wiki/How-to-Use:-Users.
Basically, just create an entry for each slot type that has a cosmetic slot kinda like this:

[[curiosSettings]]
  identifier = "<identifier>"
  hasCosmetic = false
  override = false (this property is probably not needed)

If you need any more help just let me know.