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.

Posted by: @nevadadesertskies

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Would it be possible to make the  Preview image in SubframeStudio a pop-out so that it can be resized independantly and float on top of the main screen?

Implemented in 1.0.6. 

More improvements on the management of the main window's sections coming soon.