I am sure I am misunderstanding what you need. But a circle is a “2D” shape too But maybe what you mean is it can be extruded?. If you close a spline you can extrude it too. I

I will assume you want a “3D Circle” which is a sphere with a wave cut away. This is a quick video of one way to do that. I drew the wave with a spline, mirrored it, and then extrude it. Then just subtract the sphere and the shape to get the end result.

Or do you really mean a “circle” that is warped in the Z-axis? If so I don’t know how to do that. But you can approximate it with a 3D shape that is sliced thin. So the cross section of a cylinder. It would be essentially the same thing I demoed above.