You would create an swf that would load the same shared object that your game loads. It would put the shared object in some textfields or something, and you could edit the textfields. You could then have a button that would save the shared object in the way that you changed it.

So lets say you have a shared object and it has one variable. You would have an swf that loads that shared object and puts that variable in a textfield. You would then type/change the textfield however you want, and press a button. The button would then change the shared object to what is in the textfield. This way, when you reopen your game, it will load the changed variable.

Hope that helps.