Apple Notes data is stored in a SQLite database. Some month ago the data has been stored in the file
/Users/<user>/Library/Containers/com.apple.Notes/Data/Library/Notes/NotesV7.storedata respectively
NotesV6.storedata for the prior version. The notes have been stored in a HTML subset in clear text.
Then Apple kept the file but didn't update it anymore. Instead, a new location was used:
/Users/christian/Library/Group Containers/group.com.apple.notes/NoteStore.sqlite. The data is not
in clear text anymore. I needed the access badly, because my MacBook Pro was defect (spilled a bottle
of wine over it), my last backup was long ago and I didn't sync into iCloud.
So I found apple_cloud_notes_parser, a Perl script which showed me how to parse the data. However, they have a small bug in calculating the length of the data, so you will get only the first 27 chars or so of the note.
I decided to port the code to Java (ok, to Groovy) to be able to fix that. I could have adopted the perl script but I thought I have to strip also the HTML fragments, but this was an error. In the new format, there are no HTML fragments any more.
Copy the database (location above) to the input folder and receive a file per document in the output folder. Afterwards I created empty notes and copy/pasted the notes back to Apple Notes again (at this time with activated iCloud sync).
I also tried to copy the whole database to my new MacBook, but this didn't work.