Prefs>Display>Show App in high DPI - turning this off allows me to drag plugin windows to the 2nd monitor.
Under Windows, when you use monitors which have different scaling, you should better use
- WaveLab >= 10.0.30
- high DPI ON
Else you encounter the kind of problems you mention.
Here I run with 3 monitors with 3 different scaling: 100% (main screen), and 150 and 200%
I have rarely any GUI issue.
You should better have a stable layout too: keep the same windows on the same screens rather than moving things around.