(I haven’t looked at your model - can’t download it at work.) Assuming that the exterior walls are components or groups, they can be assigned to a layer named something such as “Exterior Walls”. Then you can toggle the visibility of that layer in order to show or hide the associated geometry. The same technique could be applied to an entire floor - assigning all of the floor’s components and groups to a layer such as “Floor 2” etc.
I have not done much with cases where a given object is affected by multiple layers (for example an exterior wall component that is directly associated with layer “Exterior Walls” and also part of a group or component named “Second Floor” that is associated with layer “Floor 2”). I think all relevant layers need to be toggled visible in order for such objects to be shown.
You could also make each floor a component, and then place multiple instances of that component in the model file - one copy in-place forming the total building, and another instance off to the side as seen in your screen-capture. That way you can edit either instance of the floor and the other(s) will stay in sync automatically. (Components can be nested, so the “Floor 2” component can have wall components, furniture components, etc.)