@AndersDeleuran Once again, very helpful support.
The original problem was that that I could not find a way to turn off the isocurves for the Srf4Pt object which was created from GH. From my reading and comments received, it appeared that I had to duplicate the surface, turn off the isocurves for the duplicate, then delete the original GH Srf4Pt object from Rhino.
You have shown me the mechanism to overcome that misunderstanding, so the duplication and deletion turned out to be a blind alley. I have taken the key elements of your code to arrive at a simple and straightforward solution, which is more Python 3 than GH, but nevertheless is GH based. It might not yet be elegant, but it gives me a good start. My next task will be to modify the code to introduce reusability via general purpose functions where possible, and to introduce some curve generation and extrusion functions.
Thank you for seeing this through. If I knew how to reassign the Solution marker, it would be yours. Done. Solution reassigned.
Regards, Garry.
AddObjects.3dm (7.8 MB)
AddObjects.gh (6.3 KB)