What you want is equivalent functionality to the option for showing the notes expanded or as they are displayed at the time of printing, but that isn't provided. Use Help->Send Feedback to make your feature request, or email
omnioutliner@omnigroup.com.
If your document is not too many pages, you could just print a screen capture of the window contents...it won't be quite as nice as if rendered for the printer, but better than nothing. A somewhat more involved approach would be to write an Applescript that built a shadow document by copying only the first line's worth of text from each row. Or maybe it goes through a duplicate copy of the document and just trims all the rows, which would save the trouble of figuring out how to duplicate the document structure.