Basically, you can't, at least not with the editor. What you have to do is make it so that actor conditions go off if the mob makes a successful attack. You set up the conditions so that they have a certain percent chance of happening with each successful attack and it will end up seeming like, for instance, the dragon only blows fire every once in a while. Here's how it would work each round...
Dragon attacks with bite (normal attack) and hits.
Rolls are made for each actor condition (say you have three conditions at 20% each).
First roll is 72% and second is 16%.and third is 53%.
First condition,,,, Breathe Fire, does not go off.
Second condition, Claw Swipe hits.
Third condition, Tail Swipe, does not go off.
The next round the Dragon attacks with a bite and misses
Actor conditions do not activate so there is no percentage roll.
Third round the Dragon hits with his bite.
Condition roll, 36, 9, and 18.
Fire Breath misses.
Claw Swipe hits.
Tail Swipe hits.
Get the idea? That's the closest you can get creating mobs for the editor as far as I know.
