Hi Niko,
thanks for using biographer. We were actually looking into it already
but havn't come up with a good solution yet. At the moment we simply
add two edges in different directions on top of each other.
Of course, it would be desirable to directly support it on one edge. If
you like you could also have a look at the code as I cannot really say
how fast we will get it implemented. (the edge markers are defined in
connectingArcs.js and attached to edges in abstractLine.js).
All the best,
Thomas