Description:
Although you can add values to any item using datapacks, it just tedious to make 500 (just an example) or in general a lot of .json to have custom values

Examples of functions for kjs:

• removeAll() -> removes all values from all items
• remove(item) -> removes the values from an item given the id
• add(item, array_of_values) -> adds matter values to that item (like if it had 50 quantum and you add 10, it goes to 60)
• addAndReplace(item, array_of_values) -> sames as doing remove and then adding the mstter values (useful fro largemodpacks imo)
• getItemsByMatter(type_of_matter) -> returns all items with that type of matter

Startup (since you said on an issue that its a registry):

• registerMatter(name, icon) -> adds a new matter to the registry or if its already there, replace icon
• deleteMatter(name) -> deletes that matter type from registry

These are just some examples i can think of