Q: Backing up Notes.app content (on the iCloud / OSX / iOS) for safekeep? I'm wondering, how do I back up Notes.app content on OSX so that I can safely either trash it all and restart, or do future upgrades?

(The reason I'm doing this is because OSX and iOS no longer sync Notes properly..)
The content of your Notes.app is located in /Users/youUserName/Library/Containers/com.apple.Notes/Data/Library/Notes

So to back it all up you need to copy/move everything in the directory above to another location and restore it later.