I also want to do this, but I need control over where the edge exits and enters. In particular, on a flow chart, it is awkward to have it on top of a node. Is there any way to do this, say, to have the edge exit at (w, 0.2h) and enter at (w, 0.8h)? w=width, h=height of node, (0, 0) at lower left, (w, h) at upper right.