Modifying structure of the Main Navigation bar in BP Magazine

I’m looking to change the way categories are displayed in the main-nav bar in BP Magazine.

Right now it’s default: Home. About. Magazine. Community. where magazine drops down to show parent categories with flyouts for child categories.

I’d like parent categories to show in the main nav bar with a drop down showing child categories.

I’d also like to align ‘community’ and pages (about, contact etc) to the right, thus visually separating them from the blog categories, guidance on getting these elements in their own list would be good, I’m comfortable with the css from there.

I’ve found main-navigation.php but the category part is hard to understand what creates what.

In the end I’m looking for:

Home | Cat1(dropdown) | Cat2(dropdown) |…………….|Community(dropdown) | About | Contact