GGU-CAD: Bezier spline
Go to the menu item "Draw/Bezier spline". The Bezier spline is compiled from four model points (definition points), which you click consecutively with the left mouse button. The Bezier spline can be regarded as a type of curve template. One of three Bezier spline formats can be selected in the "Preferences/Bezier" menu item:

Strict
The four definition points lie on the Bezier spline.Loose
The first and the last definition point lie on the Bezier spline. Definition points 2 and 3 serve to determine the smoothing.Very loose
As for "loose", only slightly looser in terms of smoothing.
The Bezier spline is composed of several individual line segments. The number of segments can be specified.
After clicking the fourth definition point the following dialog box opens:

The locations of definition points 1, 2, 3 or 4 can be post-edited using the "1, 2, 3, 4" buttons. If the "L" button is pressed the Bezier spline is rejected and deleted. If "OK" is pressed the Bezier spline is used in the drawing. The final point is then the 1st point of the next Bezier spline. If you need a new starting point, first click the right mouse button and you can then define the next Bezier spline using 4 new points.