In play mode, many new objects are created. So how can I get those to the scene view, to be used again at the start? I've tried copy and pasting - doesn't work successfully, just gives colliders, no objects.
it's not possible, you should create an editor script to do this. simply create a menu item in your script and when the menu item is pressed instantiate what you want. creating a scriptableWizard is a better option and is easy and reusable.