Try Select Edges, that works for me, at least in version 7.0 update 10. It's a bit nitpicky when trying to select an edge in plan view because it often picks the top slice edge instead of the vertex of the element.
I have a question myself (sorry for hijacking):
Regarding saturated-unsaturated flow conditions, how do I go about constraining the multi-layer well to prevent it from oscillating when dewatering? Seems like the only option is to use seepage face boundary conditions instead.
Thanks,
Adam