You can make combos of object, but doesn't seem to serve any real purpose other than organization...
I'm attempting to combine two static objects and rotate both of them so that they rotate relative to each other...
combining things is great if you have to copy paste a lot, like for the asylum, I had to combine each cell piece and duplicate it, its helpful in that respect, other then that, it serves no real purpose other then keeping things joined for managing multiple pieces
I think the key you're looking for is B. Select two or more objects and press the B key, this will make them a compound object. Compounds are useful for quickly duplicating a large amount of objects and mirroring them, to make say, the other side of a room.