I can't seem to find a solution for this.
Do I really have to put in every Non-Consumable In App Purchase on its own? Is there no way to load them from somewhere into iTunes Connect?
The only workaround I found was adding a currency to the app, and then letting the user buy currency and then the items. In that case I'd only need a few consumable In App Products. But I don't know yet, if my company wants to do that.