Microsoft have updated the SteamVR with bug fixes. Update 1.1.221 fixes problems with the SteamVR and Windows Mixed Reality, it fixes the blurring of the SteamVR dashboard as well as fixing the problem of the SteamVR menu not activating when using SteamVR with WIndows Mixed Reality.
The update is available via the Steam app.
Fixed an issue resulting in some graphics layers (such as the SteamVR dashboard) being blurred.
Fixed an issue where the SteamVR button in the WMR mini menu wasn’t causing the SteamVR dashboard to activate.