Yes, it shows in File Explorer.
In Opus, it is shown in the folder tree -- using a CD icon instead of the normal drive icon.
I've tried using mountvol and get the following results:
mountvol H: /d -- system can not find the file specified
mountvol H: /p -- the device is not ready
Also, I tried the mountvol /r -- and although it did not complain or error out, it did not accomplish anything.