Notes.app uses the first line of text to generate the name of a Note. If the line is too long, the name is truncated.
When you import from Notes.app to DEVONThink Pro Office, each newly created document has the same name as the OS X Note: the first line of text, sometimes truncated. In the new document, the first line of text that was in the original Note is omitted.
This means that not only is the first line of text missing after importing, you can’t reconstruct it from the title of the note. That information is just lost.
OS X Note
DEVONThink Import from Notes
As you can see, the entire first line is missing from the imported Note, and cannot be reconstructed from the title. It’s just missing.
This is a big data loss bug, and makes it impossible to use the Notes.app import feature.