BSPLINE_MOVE_CONTROL_POINT moves control points in any specified B-spline.
---->(BSPLINE_MOVE_CONTROL_POINT)----|B-spline|----+ | +--------------------------<-------------------+ | | +-----------------------<-------------+ | | | +--+--|control point|----|new position|--+---->
BSPLINE_MOVE_CONTROL_POINT [specify B-spline] [pick existing control point] [pick new position] [pick existing control point] [pick new position]