I have an assembly that I need to show in a closed and open state. I've attached a dummied down assembly that is similar to the assembly I want to open. If you look at the picture attached I need to move the blue side away from the red side. However I may have made a mistake by the way I assembled them. The transparent red and blue parts are an assembly that was put in the main assembly.
Make the "cavity" set to distance in the constraints. Then set a relation to the value of the distance at your top assembly level. If you need both states at a next level assembly, do this with family tables.
Of course, you can make the relations smarter to use it at the next level as well.
For some reason, I still have a hard time using flexible components to drive assembly constraint dimensions.
How about just creating an exploded view? If it's merely a visual aid, create an exploded view, set the distance and you're done. It can also be shown in its open (exploded) state in a drawing. The downside is that it's not adjustable with a parameter.
Family tables are easiest to create, but I hate Family Table Assys.
If you need a stand alone model:
Hope this helps.