When a Link is selected it shows a green "+" button that when clicked creates a new Node and splices it into the link. It does that by reconnecting the existing link to the new node and creating a new link to go from the new node to the original destination of the selected link.

When a Node is selected, if it has exactly one Link coming into it and exactly one Link going out of it, then it shows an orange "X" button. When clicked it removes the node and the outgoing link and reconnects the incoming link to connect with the original destination of the outgoing link.

All links are relinkable and resegmentable.