This is really important to me too.
I started a topic on the old forum, which was replaced by this new one about 2 weeks after.
I have 2 GPU’s, I keep the more powerful (RTX 3070 Ti) for gaming in the motherboards primary slot, however this ends up as GPU 1 in windows, This works fine for everything but spacedesk
The 2nd card, a 730GT, so some reason loads into GPU 0, however spacedesk uses this card for the wireless display, which causes stuttering.
There is no way in the BIOS to change this (check with the manufacture) (and I can see why a laptop would have problems).
So, this feature to change the GPU in use, is really important.