So basically RecipeManager#getRecipeCategories only returns categories that are visible, the java doc does say returns an unmodifiable list of all Recipe Categories, so I'm not sure if this is intended.

The check that causes this is here:
https://github.com/mezz/JustEnoughItems/blob/1.16/src/main/java/mezz/jei/recipes/RecipeManager.java#L161

Is this method meant to only return visible categories?
If yes, how would I go about / could a method be added to retrieve all categories regardless of visibility?

Sorry it took me a bit to get back to this.

Seems to be working!

Thanks!

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

Thanks for the report!
I have added some new API methods in this commit to expose the data you need.
Please let me know how they work out for you:
7413f0c