I have the same issue: I have tried my best to manually edit files in the AppData\Roaming\Microsoft\Windows\Themes directory but none of the solutions I have found online work. Replacing the transcodedwallpaper file does nothing, Windows will just compress it again. Replacing the cachedimage...
I have a number of different drives that I use for different purposes but I only use two of them frequently. I would like for the others to enter sleep mode when not in use, but never my main two. Is there any way to edit power saving settings for individual drives?