1. Start as many new characters as you need. Move them to your USB.yes that would be greatly appreciated. whenever you can, no rush
2. In Horizon, extract the new saves (Savexxxx.sav) and save them on your desktop for now.
3. Make sure to have a Savegame.sav on your desktop to use for temporarily storage.
4. Open the save you want to clone in Gibbeds. Make your changes, remember to make a new name and randomize the Save Guid. Save this in your desktop savegame.sav.
5. Open Horizon again. Drag one of your dummies in from the desktop and change the name if you want. Go to Content and replace the savegame.sav with the one on your desktop. Save, resign and rehash and store on device.
Rinse and repeat.