Sharing an Inheritance (Generalization) Connector between Subclasses


I am trying to share a Generalization association for SuperClassA to both SubClassX and SubClassY, and it seems it is not as easy as one would expect.

I want only one triangle displayed at SuperClassA, with two ends at each SubClass.

Does anyone know if there is an explicit way of telling the relationship should be shared (like a merge or group option), apart from simply superimposing the arrow connectors (or using the layout option)?