Thanks,
R0J0hound! I'll use your advice:
So it seems a good solution would be to create a layout, put one instance of every object, and move that layout to the top of the layout list.
It still ***** that there's no easy way to find the current default instance. In a big project I often waste a lot of time looking for it.
Another similar problem is finding the layout where a global layer is defined. Why do I have to open every single layout and check if the layer is overridden there or not?