If you need to rapidly switch back and forth between expansion / concealment of all notes in a large document, you can use an applescript like:
--
Code:
tell application id "com.omnigroup.OmniOutlinerPro3" tell front document set note display to in line set refNoteRows to a reference to (rows where note is not "") set blnExpanded to not (note expanded of first item of refNoteRows) set note expanded of refNoteRows to blnExpanded end tell end tell