Can an EllipseSelector be drawn in an existing axis with initial width, height, and center coordinates that the user can subsequently manipulate? As far as I can tell, the only way to use the tool is for the user to manually create a selector object by clicking and dragging on the figure.
I found the answer to my own question. A similar question was asked on Stack Overflow regarding the RectangleSelector. The answer is here:
Doubtless I am one of few looking for this feature, but I hope this is helpful to someone.