The boxes the edge is drawn between (a collapsed ancestor stands in for hidden states).
How it's routed.
OptionallabelWhere the label sits (centre = middle of the rect), if the transition has one.
Orthogonal polyline, arrow at the last point.
The transition's actual target (one EdgeLayout per target).
The box the arrow points at (the target, or a collapsed ancestor standing in for it).
the transition
One routed edge: a transition to one of its targets.