“since Matinee can only be used in the Level Editor, I need to find a way to “call” on it through the Actor Blueprint.”
Are you sure that Matinee can only be used in the level blueprint? Or is it really that you don’t have a handy reference to it in your actor blueprint? Isn’t the matinee actor an actor like any other actor in the level? What if you could get a reference to it as described in the link below?
https://docs.unrealengine.com/latest/INT/Gameplay/HowTo/FindingActors/Blueprints/