Manual sort information cannot be saved on things like FAT32 drives.
If the first option is off, you cannot even turn on manual sorting when on a drive where it cannot be saved, to prevent you from spending time organising things only to find that you cannot save them.
If the option is on, Opus will let you turn on manual sorting in such a drive, and you can re-arrange the files, but the sort order will be lost when the window is closed.
In either case, the way manual sorting is turned on and off remains the same.
Since manual sorting is part of the folder format, if you want it on by default you should turn it on in the relevant folder formats, and then it will be on as soon as you go into folders which use those formats (assuming it is allowed for the type of device they are on).
"Manual sorting" option on Display tab is greyed out for Local Drives and User Default formats. Does it mean that I can't enable manual sorting globally?