I have an mxGraph, and my edges use an OrthoConnect style so that the arrows of the edges correctly point to the vertex. I found with other styles, they remained horizontal even when connecting to the top and bottom of a vertex. The OrthoConnect lets arrows point correctly.
Anyway, I have two edges coming out of one vertex, going to two different vertices. However, one edge goes right through a vertex:
Ideally, this would would branch down around where the …