There is currently no way to create a custom EntityDamageByEntityEvent due to the fact that *EntityDamageByEntityEvent​(Entity damager, Entity damagee, EntityDamageEvent.DamageCause cause, double damage)* is deprecated and *EntityDamageByEntityEvent​(Entity damager, Entity damagee, EntityDamageEvent.DamageCause cause, java.util.Map<EntityDamageEvent.DamageModifier,java.lang.Double> modifiers, java.util.Map<EntityDamageEvent.DamageModifier,? extends com.google.common.base.Function<? super java.lang.Double,java.lang.Double>> modifierFunctions)* is using EntityDamageEvent.DamageModifier which is also deprecated.

I was not sure if I should flag this as bug or feature suggestion...?
Thanks for considering.