Apologies, I overlooked that detail!
Neither does anyone else, but IMHO the problem lies with Windows 10. Even some of Microsoft’s own products exhibit strange behaviour, for example, if you’re working on the hi-res display and summon up a dialog, it appears on the wrong (lower-res) display at a huge size.
I know what you’re going to say – it only happens to you with these two applications, and yes, it’s accepted that currently both Cubase and WaveLab have Hi-DPI issues – but, in my experience Windows 10 still has significant problems handling multiple displays with different resolutions.
Me? I’m pragmatic so I got rid of the Surface Pro and now use only dispays with matching resolutions; it’s not worth the hassle of swimming upstream all the time.