If you use FTP client (I like Filezilla works really well) you could connect to the switcher(s) and the USB drive(s) then you would be able to copy the Custom Controls.
When you open it up in the FTP client you will find all of this under USB/Switcher/sets/ShowNAME/Customs Notice that the default show names are SET0-SET9. However you can always rename those folders or create new folders under Sets folder that will appear on the panel now.
So that is the "disk" access method that will allow you to find all of the individual files -- So Bank 1 Custom controls would be CC101-132 and 2 is 201-232. etc....
If you want to put it in another folder that already has a 101 but you want have it in 301 then copy the file to your computer -- rename it 301 and then copy it into the destination show folder.
#Carbonite