Hello,
I got the answer from a similar post in forum here. Anyhow I am sharing it also here, hence there might be other user falling into that whole. As I could find out in order to see, how modifiers impact stock, it is mandatory, to have a a recipe for the main product also! Maybe there could be a warning included in the next version, checking for that condition! Anyhow, good to see, that it is possible, now I just miss howto avoid getting negative stock entries, since I cannot see a case, where it makes send to be able to sell products, that are physically not in Stock.