Combat jellies and potions

I would like to be able to set when the jellies and potions take effect. For instance... Using Branchy or other healer type, why would you want it to go off at 50hp? when you still have 3 heals and maybe opponent isnt damaging you a lot each turn...???

I have jellies on my branchy for the "just incase" time that Haypi throws that wildcard at you