Backing up is the best way to preserve data but this isn't very flexible - so I understand why you'd want a different approach.

What you could do is:

1) First save your user area to a user file (so you don't lose it when you wipe it during the next steps)

2) Initialize only your user area to clear it out -- since you have a user file "backup" created in the first step

3) Library import any Library you want to backup. This copies the library to the user area.  You get to select which Performance(s) you want to copy.  Select all.

4) Save your user area (again) to a user file which now contains your library.   Optionally, you can save as a Library file if you want to do that instead.

... next few steps are optional, but for sanity

5opt) Initialize only your user area, then load your user file which has the copy of the Library

6opt) Check out different Performances in the user area (filter by bank: user) and make sure the key Performances you want backed up are working properly.  If they aren't then you may be trying to make copies of protected commercial or promotional libraries.  In which case you would have to have the original distribution files you used to land these Libraries in the first place.

7) After satisfied everything is OK - delete your library you now have a user (or library) file for

Yamaha didn't provide the easiest-to-use file system.  There's usually lots of steps which is why making a complete backup is a good thing to do even if you, in addition, try other things in order to give you more flexibility down the line.