This raises an excellent point - especially if someone typically uses the simple mode, they may not be aware, or even forget, that there is advanced mode and that it might be necessary to do what they want.
If I might throw another option into the mix: it would be helpful to have either a toggle switch, or at least a reminder, on each page that has features hidden in the the advanced section. This could either be in addition to, or replace, the global advanced mode.