I'd like to move a drive letter from the normal folder string of drive letters to the "Favorites"
In the screen shot below, I would like to move drive letter R: to "Favorites". The key here is "Move". I do not want to see it under "This PC"
Sorry, I think I was incorrect. It only affects what you see under This PC in the file display, and not the folder tree.
I don't think there is currently a way to hide a drive from the folder tree, other than by removing the drive letter from it entirely (which is not what you want for the C:\ drive).