I could be mistaken as I've not really used it before, but I was under the impression that Quartus only has a state machine viewer - i.e. it can spot state machine like logic and display this graphically. However because it produces this diagram from the logic, it would be misleading to allow you to edit and save.
Perhaps someone else could confirm if I'm talking a load of dingo's kidneys - it may have changed in Quartus 8.
In a previous job I used ActiveHDL which I found to be the best HDL simulator that I've used. This comes with a really good state machine editor which produces code for you. It's really intuitive and I would seriously recommend it if you can convince the boss to splash the cash.