@BearsAreCool510
Yes you can and it is already documented:
My 2070 SUPER VR settings and suggestion (Reverb G2 - WMR)
Additional Comments | Windows Mixed Reality | You can use the SteamVR OpenXR driver with any WMR headset
@LikingWindow600
To my knowledge you can’t add MS Store FS to Steam Library, not directly. This takes building a proxy impostor instead, a launcher, which will impersonate the app in the Steam Library. Not worth it though.