And finally, a last question, I am quite new to SH3D, so I may not think properly

I would want to draw wirings from the first floor to second floor for instance (and also across rooms). I did a new separate level called "wirings" to put all my wires, and I gave it a height corresponding to both floors. I am not sure I can manage to do what I wanted with this configuration. Across rooms it seems to be ok, though not responding very easily.

Any ideas or suggestions welcome.