To start, you’ll likely need to have “Enable Advanced Features” turned on in the latest-greatest version of Quicksilver.
First, to enable proxies in QS preferences… Under Catalog > Quicksilver, turn on “Proxy Objects”, “Internal Commands”, and “Internal Objects”.
To access menu items (and enable the Show Menu Items action), go under Plug-ins > All Plug Ins and scroll down to turn on “User Interface Access (+)”.
In System Preferences
Then go under your Mac’s System Preferences, to Universal Access, and turn on “Enable access for assistive devices” at the bottom.
via Enabling Quicksilver proxies and application menus | The Celsius1414 Journal.