Disabled spellbook with passive

[Keiga]

Hello I was trying the passive chapter for Daelin's Trigger Enhancing Basics, and I couldn't get the immolation part to work by putting it in the disabled spellbook, I put the immolation into the spellbook, and whenever the passive ability was upgraded, the immolation never got upgraded. I fixed it by making 3 immolations and put a different damaging immolation for each level. Is there a better way to do this? The guide never said to do this, I think I messed up somehow, here is the trigger.

Essence Burn
Events
Unit - A unit Learns a skill
Conditions
(Learned Hero Skill) Equal to Elemental Essence
Actions
Player - Disable Spell Book (Elemental Essence) for (Owner of (Triggering unit))
If ((Level of Elemental Essence for (Triggering unit)) Equal to 1) then do (Unit - Add Spell Book (Elemental Essence) to (Triggering unit)) else do (Unit - Set level of Spell Book (Elemental Essence) for (Triggering unit) to (Level of Elemental Essence for (Triggering unit)))