The shape tool is a tool for adjusting nodes. Double-click a line segment to add a node, double-click a node on a line segment to delete a node, click and right-click between two nodes to select a curve, and then use the shape tool to adjust it. You can also control the bending degree of the curve by adjusting the adjusting handle, and you can also change the direction of the line segment by turning smooth nodes into sharp points. Nodes can also align, reverse direction, and close disconnected nodes. Basically, shape tools are these operations.