User notes got converted, although I got an error message:
I/O Error #0 in the file "Bible Text Notes".
I restarted Accordance, all is fine now. Synced with the Dropbox and iOS devices. All works fine.
I noticed that now I can type Latvian text in User notes (Hooray!!!!!), but instead of one Unicode character Accordance for Mac shows two characters. At least all the other letters are preserved in the note. (Adding only one Unicode character in iOS version turns all note into garbage. Still a work to do. And I noticed that now Accordance for iOS added .acc4 file extension at the end of my User Notes file, shown in the center of the tools pane toolbar.) Now, if you could show Unicode characters in the User notes (Mac version) properly… :-)