An option is needed for NOT connecting conduits to cable trays when modifying conduit systems. Now it happens when modeling (close enough or colliding) and having the "automatically connect" mode on, which is understandable and apparently by design, BUT it also happens when stretching a conduit over a cable tray in a similar manner ( = close enough or colliding). Yes, you can switch off "auto-connect" when modeling but that doesn't help stretching, there's no option for that case.