In order to use Quest-on-PC you will need to calibrate with the LIV Connect app as usual and then use Side Quest to copy mrc.xml from Android/data/tv.liv.connect/files to Android/data/com.beatgames.beatsaber/files or other game folders
Download SideQuest here: https://sidequestvr.com/setup-howto
After connecting your headset and SideQuest, in the SideQuest desktop app click the folder icon on the top bar
Next Select Android > data > tv.liv.connect > files > save the mrc.xml file to your desktop
Now add that file to the game files folder, I will use Walkabout Mini Golf as an example here.
Android > data > com.MightyCoconut.WalkaboutMiniGolf > files then select upload file to this folder in the bottom right hand corner of the SideQuest app.