[Ken Case]

If you want to see everything you've ever entered into the OmniFocus database, the easiest way is to select "All Items" from the Perspectives menu. This resets your view bar settings, project focus, sidebar selection, and search field, giving you a complete list of everything in the database (completed or not). You can then use the Search field to find things within this list.

(Note that this doesn't include any old data you might have moved to your archive; to access your archive, select "Open Archive" from the File menu.)

OmniFocus also supports Spotlight, so you can also search for items using the magnifying glass in the top right corner of your screen (in the menu bar). Unfortunately this only searches active projects at the moment, though we're considering extending this to also search inactive projects and the inbox.