Editable tween curve on surface or polysurface

History in Rhino 7 must be turned on, in order for the modifications on the input surfaces to affect the output tween surface and its corresponding curve intersection. The latter could be further simplified via the "! _RemoveMultiKnot" command, though that will destroy the history and also may cause the curve to no longer sit perfectly accurate on the surface/polysurface.

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