I did read this 5 times now, and still I have no idea, what you are talking about.
What exactly is the purpose of this trigger? Is this a tutorial or is it a question? What does the ability do? What is the Hero Veterancy you use in your condition? What behavior are you talking about?
With data, you would want an ability that when you press the hotkey it would swap the ability with a second one which uses it on your hero.
Then you either select the target for the first ability, or push the hotkey again to use the second swapped ability.
You're on the right track, but I don't think you can "swap" an ability... and in any case, just swapping the ability wouldn't work. To make something like this work, you need to add both abilities to the unit via the Data Editor and use a buff & requirements system to show/hide the proper buttons (or triggers.) One button would be for the targeted ability, and another would be for the self-cast ability. You might be able to accomplish the same effect using scripts as well but... that's not my field of expertise ;)