This is from http://yed.yworks.com/support/qa/3816/how-to-share-re-use-edges
Making it so edge labels can have multiple in/out connections would likely break lots of yEd, so this would only be a layout option.
In the common case with a node that has multiple related nodes, it greatly cuts down on visual clutter to combine edges wherever possible. Using "bus routing" tries to overlap the edges, but this would be one step more involved:
Edges with the same label, and either the same set of starting nodes, and/or the same set of ending nodes, would be "combined"
Only one of the combined edge labels would be shown (or they would be arranged directly on top of each other, making them appear to be combined)
existing standard layout
same structure using proposed edge merging option layout