Thank you for answering! But I am not really looking for a workaround.
With Rhino 5 (And still in Rhino 6…until a next update!) it was possible to just hide the “backround bitmap” in the model area and show it in the detail area without any extra layers needed to make visible/invisible. So you can make a screenshot of the actual model and the bitmap in the layout view without seeing the bitmap in the rest of the model views.
See attatched picture. (Layout as floating window)
As this is a very easy solution I would just like to know if anybody has found a way to make this work with the new picture command.