Under “Add Pathfinding to your game” (under chapter 13 „Planning Routes and Creating Believable AI“) there is a paragraph about add/editing/removing nodes/connection.

"„To remove a node—contrary to the on-screen instructions—you need to right-click it; this action deletes the node immediately. There is no undo, so be careful.“

Unfortunately I was not able to remove a node. On a Mac Book Pro there is no right-click option or do I missed something.

Bernd