Welcome, Fracesc! Please bother us with "stupid" questions - those are the questions where people learn the most, at least if they ponder the answers.

It sounds like you know about many topics in math that category theory touches on in interesting ways. For example, right now I'm trying to finish off a paper with my student Jade Master, about a category where the morphisms are "open" Petri nets - that is, Petri nets with some places designated as inputs, and some designated as outputs.