I can see how that could be useful, although this is a bigger feature than what it might seem: changes in the cockpit (main interface) when the preview is elsewhere need to be done "naturally", and the pop-up is not just a pop-up but a whole new interface that interacts with the cockpit, with the whole zoom/pan/stf/etc functionality in it. When I look into it I'll probably start by using a DPRT window (the custom realtime preview window you can find in many of my PixInsight modules), as it offers most of what I'd need.