Can you make "Coremods"?

uh, your usage of the term "coremods" might be inaccurate; the words you could be looking for instead might be: library mod (most commonly) or core mod (notice how there's a space there).

here's why: "coremod" is a term used for a special tool, or a part within a mod, that can be utilized to change virtually any part of the game, but they're not necessarily the "core" for other mods plus they come in JSON file format iirc, which mods don't use coz all mods are JAR files.

here's an explanation from the Minecraft Forge forums:

diesieben07

Coremods are an incredibly powerful tool allowing you to modify the bytecode of every class loaded by the game. However, like any powerful tool, it needs to be used responsibly or things will go haywire, even if at first sight everything works fine.

mods that contain shared data between mods depending on it are usually referred to as "library mods" by devs. but in making a library/core mod within MCreator, I'm not sure how it's done without code. correct me if I'm wrong, anyone, but tags are the only things that allow you to have "shared properties" between mods that depend on a core and made with MCreator, for now. so if you want more advanced support, you could try coding one yourself if you're up to that challenge!

With IDE in MCreator, you could make a coremod