Hello there.
Sorry for the confusion here. In an early version, I had to remove the ability for a recipe to have multiple category ingredients. As it turned out, the function never worked correctly in the first place, and caused a bunch of weird problems in the system.
The demo plugin has a very old version in it, specifically because I didn't want to have to update the recipes in the demo if I updated the demo plugin file (because of the category ingredients as well as a couple of other things). Please refer to the help documentation in the standalone file to ensure you are reading the most correct information.
Don't worry, though, as I've already solved the problem that was preventing me from allowing recipes with multiple category ingredients in them, and it's even already been released in the MZ version of the plugin. I am working on backporting it to this version currently. As this breaks compatibility with the Recipe List extension, I need to fix both, and I need to verify the fix doesn't break either of them, so it's taking a bit longer than usual. But the issue is fixed and it's coming soon.
-Ramza