Is there a way to have the algorithm spawn a specific pattern at the intersec point of two other patterns? E.g. have two fractal patterns and where they intersect it should create a circle pattern on top?

I'm sorry I don't understand what you have in mind. If you mean that the third pattern should only exist where the first two intersect, that sounds like taking the intersection of three patterns. If you mean making some kind of copy of the whole third pattern at every place where some condition is satisfied, then there is nothing like that because a pattern in general is as big as the whole plane (among other difficulties).

If you can be more specific about the end result you are looking for, maybe there's another way to get something like it. It sounds like you are trying to make circular islands that are scattered semirandomly? That is not easy to do right now but I can keep it in mind as the sort of thing to work on in the future.