Extactly what the title says.

I was doing some sketching when I relized there is no option to snap in the midoint of an ellipsoid arc. To make my question more clear and specific, I'm looking to snap / find the midpoint any random ellipsoid arc or spline, not the the mid angle. So, is there any way to achieve this?

I need method that will work in both 2D and 3D sketches, like a 3D sketch spline or a projected curve on a 3D surface (in my case)

Thanks.