As Chris/@overover said, you can save all of the Registrations (plus User Songs and User Styles) to a USB flash drive as a User File. It's essentially the same as a Backup File, except it doesn't contain any of the backup data for settings that are automatically preserved and restored even when you turn the keyboard off and on.
Two other important differences between a User File and a Backup File are that (1) a Backup File can only be saved and restored using the Yamaha Musicsoft Downloader program on your Windows computer or MusicSoft Manager app on your iPad, whereas a User File is saved to and restored from a USB flash drive; and (2) you can have only one Backup File-- unless you keep different Backup Files in different folders or temporarily rename them so you can have multiple Backup Files-- whereas you can have up to 100 User Files on a given USB flash drive-- or more, if you use different folders to store up to 100 User Files per folder, or temporarily rename them.
Note that renaming the files or storing them in alternate folders can be problematic, because the names must match what the keyboard is expecting to see or it will ignore the files, and the files must also be in the expected folders, so temporarily renaming or moving the files will require renaming or moving them back again before you can use them.