I tried this already but the result was graphically not very pleasing, i.e. clean to me and it didn’t communicate what I wanted to express. The diagram I had in mind was rather prototypical: three ellipses situated in the corner of a virtual triangle connected by double-sided arrows. My solution was to create a prototype for an intermediate node which expresses an interdependency. I placed the node in between the other nodes an connected them accordingly.
Nevertheless: thanks again for your suggestions!