I think I was going about it the wrong way, in the Level Blueprint you don’t need to store Static Mesh Actors in variables that already placed in the level. Every time you require a reference you simply select the Actor in the viewport, right-click in the Level Blueprint and click on Create a Reference to “YourActorName”.
For example:
http://i.imgur.com/pVxfe07.png
In other cases you would need to assign references to variables, for example if you are spawning Actors with blueprints.