Sorry, separate point:

>Mesh formats like stl cannot represent a circle by its position and radius, while a parametric format like step can.

This is where I think the Geometry nodes can help. A node (function) can be used to represent the circle with inputs and outputs set or changed as required.[0]

I have not fully explored this space though and so my "hopes and dreams" may well be as useful as thoughts and prayers...

[0] https://docs.blender.org/manual/en/latest/modeling/geometry_...