Hey -
In your case of a button that open a door, rather than getting a reference to the door when the button is pressed it would probably be best to add a variable to your button blueprint that holds a reference to the specific door it is connected to. For example, if you create a Door blueprint and a Button blueprint, you can add a variable of type Door to your Button blueprint and make the variable public. When you place the button in the world, you can set any door that exists in the level to the variable. When the button is pressed, the logic that controls the behavior of the door is run only for the specific door.