PreGameplayEffectExecute

Overriding PreGameplayEffectExecute in your class derived from UAttributeSet will allow you to modify incoming Gameplay Effect magnitudes before they are applied. This is a great place to modify incoming transient attributes like Damage, Healing, etc.

How to check the incoming attribute type

UProperty *DamageProperty = FindFieldChecked>UProperty<(UOWSAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(UOWSAttributeSet, Damage));

UProperty* ModifiedProperty = Data.EvaluatedData.Attribute.GetUProperty();

// Is Damage about to be applied?
if (DamageProperty == ModifiedProperty)
{

}

In this example UOWSAttributeSet is the name of your derived class.