@GrecKo Thanks for the tips.
Initially I had a QList with c++ objects, but now for simplicity I am trying to avoid that. To manage the dynamic objects, each has a signal connection when they are created. Then when something happens, they receive signals and each object manage it self (turns visible, unvisible, gets deleted, ....). I think this approach it is much easier than creating filters and lists or repeaters.

You could use a QRubberBand to setup the line and once you release it add the QGraphicsLineItem to your scene.