IntelliJ resolves library when proofing but doesn't when compiling

I have set up my project like this: https://discourse.processing.org/t/writing-processing-in-kotlin/3957

When programming, everything works fine and the proofing works. I can find all the classes from the library. However, when I try to build the project, suddenly it doesn't find anything from the classes I imported.

Basically, what I did was I first added the folder as a library and then I added this library to the module main. I'm adding a screenshot. How could I make the compiler see the library? Or is there any other issue?