I've never found a way to edit that menu. Nowadays, I almost exclusively use
LaunchBar. You just select the file you want to open, hold down the LaunchBar shortcut (control-space for me; I think it's command-space by default), and then when LB opens up hit the abbreviation for the app you want and the selected item gets opened.
I think the functionality is called "Instant Send" if you're looking for it in the LB promotional materials or documentation.