Pulling Windows Desktop apps into VR should also work for Rift connected via Displayport to HDMI adapters
Users of certain gaming laptops (e.g. ASUS ROG G751JY) cannot operate their Rift via the HDMI output due to some technical limitation. However, the Rift works very well when connected using (certain) displayport to HDMI adapters. Since this is working I am quite sure there is no hardware limitation for Oculus Dash not being fully functional in this specific setup.
It seems that Graphic Drivers (Nvidia 390.65) do not recognize the Rift when connected via Displayport (=> HDMI) and therefore the virtual "Nvidia VR-DESKTOP" display device is not created when connecting the Rift.
Actually, I found out that it is possible after all to pull Windows Desktop apps into VR also for users whose Rift is connected via Displayport to HDMI adapters! For me the problem was apparently that within the Windows (10) Multidisplay configuration the "Nvidia VR-Desktop" for whatever reason was set to be a "Duplicate" of my laptop display. After setting this to "Expand" (while leaving my laptop display the primary one!) it finally worked! However, it took me a lot of try and error to find this out as I wasn't aware of that "Nvidia VR-Desktop" display device until I started the Oculus Software and at the same time had a look into the Nivdia Control Panel multi monitor setup where I finally saw the "Nvidia VR-Desktop" display showing up.
By the way, when connecting my Desktop monitor to my laptop via HDMI (plus the Rift on the Displayport) I could not find any way to let the "Nvidia VR-Desktop" device show up in the Nvidia Control Panel.
Thus my "adjusted" idea for an improvement would be to not let run users into this issue: either by making sure that the "Nvidia VR-Desktop" display device is forced into the correct multi monitor display mode or by documenting/describing this somewhere.