Make Source and Target bi-directional

[jens-abc]

Hi. Is it in anyway possible to make the source_position and target_position be bi-directional, or even better, make all 4 positions take any kind of connection.

Right now it can be a bit of a challenge for non-linear flows.

[Piaskun]

That would be useful (dropping input/output notation), but I think that would need to be bundled with multiple port, as now system doesn't ask for specific port, since there are only one source and one target.
Adding something like this: https://reactflow.dev/examples/layout/elkjs-multiple-handles would require you to target specific port on node, and then whole source & target convention can be dropped.