[Hover to show help]

• CTRL + click a node to show the modification helper
• Move a node by dragging the aforementioned modification helper.
• Resize nodes by moving your mouse to the edges of the modification helper. When your cursor changes, click and move the mouse to change the node's size.
• Hide the modification helper by clicking it while holding the CTRL key.
• Add edge handles to a straight line edge by clicking on it.
• Enable modifications of splines by holding CTRL and clicking on the spline. Treat the blue dots like any other node, e.g. CTRL + Click or drop it.