Selecting a node will show a rescaling handle that when dragged will modify the node's GraphObject.scale property.

Just as the ResizingTool changes the GraphObject.desiredSize of an object, and just as the RotatingTool changes the GraphObject.angle of an object, the RescalingTool changes the GraphObject.scale of an object.

This extension tool is defined in its own file, as RescalingTool.js.