I’m not sure how to describe what I’m looking for except through the examples below. This is a kind of shape that’s often seen in vine inspired motifs. It’s similar to a spiral in that the rate of curvature is changing, but the change isn’t constant, and sometimes it changes to the other direction.

Does anyone know a good way to procedurally create these kinds of curves?

What are the constraints and requirements for the curves. NURBS curves by placing control points tend to be smooth and can be almost any shape. The higher the degree the smoother the curve will tend to be but the more difficult to change the shape locally. Note that for curves created using interpolation (curves through selected points) the higher the degree the more the curves will tend to develop oscillations.

I assume you only use Grasshopper and not Rhino by itself. To learn more about NURBS curves you might try creating curves directly in Rhino by placing control points, and then moving the control points. Use the Curve command and experiment with different degree curves and number of control points.

Then you can experiment with creating curves using Grasshopper.

Find a geometric arrangement of control points which produces the desired family of curves and can be desribed by a small number of parameters. Use the parameters to create the network of control points, and then create the curve using those control points.