An NSPredicateEditor can be set in compound mode, using the IB or in code
[predicateEditor setNestingMode:NSRuleEditorNestingModeCompound];
The user can then hold the 'option' key to add another compound line, to generate complex filters like
((A AND B) OR C)
Some users may figure out how to do this in about one minute after reading the app documentation, in five minutes after searching the web, or perhaps they'll never learn it and ditch the application altogether.
I would like to have some suggestions on building a user-friendly way to use multiple compound lines in NSPredicateEditor.