### Function: SetSpellDisplayEffect(spell, idx, field, percentage) **Description:** Set's the spell display effect value. **Parameters:** - `spell` (Spell) - Spell object representing `spell`. - `idx` (uint32) - Integer value `idx`. - `field` (string) - String `field`. - `percentage` (uint8) - Integer value `percentage`. **Returns:** None. **Example:** ```lua -- From ItemScripts/AbbatoirCoffee.lua function cast(Item, Player) Spell = GetSpell(5463) Regenz = 18.0 newDuration = 180000 SetSpellData(Spell, "duration1", newDuration) SetSpellData(Spell, "duration2", newDuration) SetSpellDataIndex(Spell, 0, Regenz) SetSpellDisplayEffect(Spell, 0, "description", "Increases Out-of-Combat Power Regeneration of target by " .. Regenz) CastCustomSpell(Spell, Player, Player) end ```