In the Tools tab, you can turn on Create a recordable window. VirtualDesktop will now be able to stream this window to your headset. The issue is that your VR display (VirtualDesktop) must have a compositing option to display this recordable window above the desktop. This is easy with OBS, but most VR software don't have this.
What you can still do is to : censor screen A with HotScreen, put the recordable window on screen B, then set the correct screen latency to 1, and use VirtualDesktop to stream the screen B to your headset. You won't be able to interact directly with screen A, however.
Sadly I can't fix this, this is a limitation of Windows. But we only have to wait/find a VR program that allows window compositing to make it work.