One discovery when I started the live D3 version of the space view was that having arrows (example from an early prototype) ended up looking cluttery/claustrophobic, particularly with nodes that had many many inbound relationships from other nodes.

Ultimately I’d like arrows to be something you can turn on and off, because there are some use cases where I feel they’re less annoying. But I wonder if there’s any other minimal way of indicating directionality. To that end, one idea I just had was to have a relation line touch the node on the sending end, but stop short of the node on the receiving end.