The existing shapes are accessible through the shape layer drawing surface (e.g. map.layers.surface
I'll provide an alternative for the moment, as this part of the API is still unofficial and subject to change. It will be made public for the next release.
My suggestion is to store a reference to the desired shapes in the shapeCreated event. Those are live objects that will respond to changes in fill, stroke, etc.
Does this make sense?
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