Interesting question. The methods for selecting and moving one vertex, referenced by some index if not directly by X and Y, are in fact present in the Poser Python. The hard part, I think, is in using the mouse, because Python doesn't have good communication with mouse moves in the document window. I've been looking at this set of actions for a different purpose. One trick that might work is to use a little prop, created by the Python script, as a kind of 3D cursor. The position of this object in X,Y and Z would be available to Python. You would drag the little cursor thing to the desired location, using regular Poser editing tools; Python could then locate the vertex and apply a parameter dial to its location.

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