1) Make sure that "child notes" is enabled for copying between libraries in the General pane of the preferences.
2) If you copied the items previously without notes, you'll need to delete the items from the target library and empty the trash, and then drag again. (This won't be necessary in a future update.)
2) If you copied the items previously without notes, you'll need to delete the items from the target library and empty the trash, and then drag again. (This won't be necessary in a future update.)