I think that many Rhino users would benefit if there was an option to build a circle whose diameter fits between two end curves in a tangent manner, and its center lays along the tangent of a third curve. Basically “Circle: tangent, tangent, center along curve”. To better describe it, I will post an example below. Neither “Circle: tangent, tangent, radius” or “Circle tangent to 3 curves” could do that.

I made the icon for “Circle: tangent, tangent, center along curve” by modifying the icon of “Circle: tangent, tangent, radius”: