Yes I agree this would be useful. Having to use key combinations or similar to view instruments which are often too small to view in normal cockpit view can be distracting especially for example monitoring speed on approach. I think it would be very useful to be able to drag a copy of an instrument to another screen and if necessary increase its size. Admittedly it is not very realistic to glance left or right to read an instrument but possibly more realistic than using a key combination.
Thank you, the link you provided to the youtube video was very useful. By watching this I discovered that you can create a separate window of some instruments by using the AltGr key and mouse click. I already have a second windows screen that I can move the instrument to but it is also useful to know about Spacedesk.
This leads to the question that as I was not aware of the AltGr facility, how would one find out about this except by pure chance? I am not aware of any help files which describe this. It is a pity that it does not also work with analogue instruments but at least this helps me with the glass/digital screens which are sometimes too small to read in normal cockpit view.