UPDATE: I tried various things at random, and finally got it to be moveable. I don't know exactly what I did, but the VP window is now on my second monitor where I want it.
---------------------
I know this used to be possible, because it's the way I worked in earlier versions of Vegas Pro. I'm now on VP20 on Windows 11 - also on a new computer. My Preview window is taking up lots of real estate on my primary monitor, and I can't find any way to move it to my second monitor. I know I can use the second monitor as "external device", but then the preview takes up the entire screen of the second monitor, and I can't access anything else I keep on that monitor.
(Another forum said click/hold the window name and then drag it... but that doesn't work. Maybe it did in earlier VP versions?)
I hope I'm missing something obvious, but I can't figure out what that might be.