In the top right corner of the editor there's a drop-down box that picks between Mission, Intro, Outro-Lose and Outro-Win. As long as the mission is ended through one of the possible #End numbers, Outro-Win is run - if it's ended through Lose, Outro-Lose is played. That, at least, is my experience.
Not sure what your problem is, really, as long as you're editing it in the correct "space".
Wolfrug out.