Hide submenu for non-members

Hello,
I am teaching an online course through my site. I am using WP eMember to protect the course content and only make it available to students (members).
I need a responsive (needs to work on mobile too) navigation menu for the course that only the students can see when they are logged in. This would have each lesson page in a dropdown.

I’m guessing the easiest way to do this would be to enable the submenu and somehow protect it, perhaps via this method of editing the PHP.

However, I’d like to avoid that if possible, so I don’t have to update every time there’s a theme update.

Should I use that method? If so, what specific code should I use (i.e. the slug for the submenu)

Or should I use another method? For instance setting up a menu/widget and placing it at the top of each course page (ugh), or perhaps creating a course page template that all those course pages use? OR some other, better solution?

I’m looking for the easiest, most long-term viable solution for this. :) Thanks so very much for your help. I LOVE this theme.

Technical details: I’m using the latest Enfold with a Enfold Child.