Sorry, I was reading your first post but didnt read your second question properly, I thought you were asking how to run the utitility(should have got more sleep last night
).
Anyway in this case the toggle utility isnt going to help you at all. If its not possible to change the difficulty on the manager screen I think you are out of luck.
If you are looking for a way to make the game more challenging I would suggest(if you havent already) turning ratings off and playing talent only and you can also change the trading difficulty. To do this you will have to run the MM togggle utitlity.
Personally I play manager mode with the default difficulty with talent only.