Suggestion

I'd like to make a custom gui that implements JEI's search feature, and exposing a search function through the api would be helpful. If there's already a way to do this please let me know.

Thanks for the suggestion!
Are you looking for mezz.jei.api.runtime.IIngredientFilter or do you need something else?
https://github.com/mezz/JustEnoughItems/blob/1.19/CommonApi/src/main/java/mezz/jei/api/runtime/IIngredientFilter.java

Thanks for the reply, I think it is, so long as it can have prefixes.

That's exactly what I needed, I'll close this for now and will send a message if anything is off.

Yes, this is used directly by the search bar, so it should work the same including prefixes and other operators.
Please let me know if you run into anything unexpected.