I'm not really sure what you mean by , just type what you want in, the stuff in my previous post is a copy and paste from a trigger, the skill u are trying to create needs a trigger to work.
This is because the moonglaive "ability" in normal RTS warcraft is not even an ability, it's just a modified attack with maximum number of targets changed to 2 and weapon type changed to missle bounce. The upgrade just changes the maximum number of targets to 3.
By dummy skill, i just mean an ability that you create so can click on it to learn the ability, which is actually an upgrade you are changing.
Blizzard is actually a very bad ability to use as a dummy spell because you can click on it as if you were going to cast something, i just added that in because i made that trigger fast, the best skill to copy is storm hammers, make that a hero ability and remove dependancies, or critical strike with 0% chance.
Unit learns a skill is under "Unit - Generic Unit Event"
Hope this cleared things up -.-''