Quoting the Quicksilver User's Guide: You can't save a trigger with a dynamic action. Dynamic actions are those that ask the application at runtime for their content. So the Current Application (Menu Bar...) trigger above works, but you can't do Current Application (Menu Bar...) Help.
I feel that the ability to save dynamic action triggers in QS would be the best next step to take in the next release of QS. It would free the everyday user from having to use anything but QS for interfacing with applications.
