Consider:
digraph D {
0[pos="0,0!"]
1[pos="0,5!"]
0 -> 1[label=0.25]
1 -> 0[label=0.50]
}
Rendered under neato engine, this gives:
Is there a way to increase/control the curvature of the connecting arcs so that the rendering is something like the hand-drawn annotations below:
Edited to add: While I don't have to stick with neato, it is important in my application that the node pos coordinate values be upheld.


[there may be better ways, but edges are pretty hard to wrangle]
This solution requires
neato -n(see https://graphviz.org/faq/#FaqDotWithNodeCoords) and (https://graphviz.org/docs/attrs/pos/)Different versions of neato seem to produce different results when previous answer is input. This input file should work with older & newer versions of neato.
Giving:
