This allows more interesting parametric shapes to be defined using Bezier splines.
The shape is based on a cylinder, where the radius of the cylinder at each point is determined by the spline function.
Likewise, the y value at each point is determined by the y value of the spline.
You can edit the shape using the left window, and use the rotate & zoom controls to get a better look at your shape.
Bezier Spline Editor
Parametric Shape (result)
Show Connecting Lines
Drag nodes to position them. Endpoints are color coded for slope locking.
Red means the slope is locked (continuous), and green means the slope is free.
Double click the node to change the slope lock.
Spline segments can be added or deleted using the buttons.