We’ve previously shared a Terminal-based approach for customizing the behavior of All My Files in the Finder. But in Mountain Lion, customizing All My Files’s search criteria—or the criteria of any other similar Finder sidebar entry, is deliciously simple:
Simply right-click (or Control-click, or two-finger click with a trackpad) on the sidebar entry, and choose Show Search Criteria. You’ll see the Smart Search characteristics that power the entry in question, and you can tweak and re-save the search factors you prefer.
Full disclosure: You can’t save over the existing All My Files saved search with this approach; you’re really just saving a new search instead. But it’s quick, painless, and non-destructive.
Mac OS X Hints