The fact that phones haven’t been able to to this easily/natively/what have you is wild. Similarly, the fact that you can’t use old tablets as external monitors without, in my experience of quite a few, significantly buggy software that’s got significant lag in the best of times, is pretty wild. Sure, the technical hurdles aren’t small, but damn.
I’ve got a reasonably high end newish tablet (Galaxy S7+) that I can use miracast to use wirelessly as an extra PC monitor. It works quite well… if I’m near to a high quality new router. But can I just plug the tablet in and use it as a monitor with my laptop? Not remotely well.
It’s been a year or two, maybe I should check for new software again.
I’m confused by the it in your last sentence.
Using a screen recorder (there’s a built in one in the Xbox games app depending on version of Microsoft, or if not, people always seem to use FRAPS) to capture whatever is in the window to get more information could help.
Someone else will likely be along shortly with more helpful info.