Add Control adds a control point to the spline. Place the cursor over a spline chord and watch the status bar. When it says Reference, click to place a control.
A control point is added to the center of the chord.
Delete Control deletes a spline control point. Select a control point for deletion.
The spline adjusts after control point deletion.
To move a control point, drag it to a new location.
To move spline end points, select the spline.
To move the entire spline, drag the end controls, which display as blue dots.
To modify the spline curve between the end point and the next control point, select the end control, press
Tab, then drag the end control point.