Appreciate your feedback as always, Sir!
I use the ztkbubble example as a basis for making almost any type of composite item on Zinc.
I think you missed the operative word 'complex', and I failed to explain properly as is tradition by now. Specifically I need to create objects that have one-to-one, one-to-many or many-to-many relationships. Each object has a visual representation on the canvas (filled curve in most cases); Each relationship has a visual representation on the canvas (bezier). I can figure out how to do this -- the question is if some project exists that use Zinc (or canvas) to visualize complex relationships between objects; ie how to best approach this problem in an efficient way using PTK, hopefully saving me hours upon hours of experiments and refactoring ;-)
Subclassing Zinc might be a viable option for me - I will look into this. When I understand bless(). ;-)