The presetting of the email field sounds like something that's happening your browser. Zen Cart makes no attempt to preset that field. But it will prevent you from creating the new user without a properly formatted email address.
Although Admin Profiles was more commonly used to prevent "other people" from accessing everything, the way in which you were using it, was the reason for which I originally wrote it. So your point is understood. However, you'll need to do it slightly differently going forward.
The superuser setting is designed to show everything. So to work with some menus hidden, create a profile, "Store Owner" say, that has just the ones you want and attach that profile to your user ID.
You will still need a superuser though. That's by design too, to stop people from accidentally cutting themselves off from the Admin Access menu. So you may need to create an additional user, even if they're rarely if ever used.
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(Questions answered in the forum only - so that any forum member can benefit - not by personal message)