Item Associated With Particular Treasure Chest Actor?

Hi man,
Thats super easy.

You can set any variable in your chest, to be editable, and visible from outside.

I would suggest you to create an enumerator (Random site that show you some steps : Enums in Unreal Engine 4 Blueprints - Couch Learn )
For example, create an enumerator with… “Random” , "Epty " ,“Trap 1” , “Object A” ,

Than set this variable to be editable and visible.

When you drop your chest in the scene, select it and in the detail you will find your Enumerator.
So you can set every chest with a different variable,

Inside your blueprint you can put a Switch on enumerator, to run different part of blueprint , or use it just to spawn the item you named in it.