Client requested a simple header: Logo in the center, one navigation item on its left, a second navigation item on its right, and the rest of the navigation is located in the off-screen menu (on all devices).
My thought is that I need to use the header element and hard code the two links & the logo into it, and then use the off screen menu but how would I add the hamburger menu?
that method would work.
Simply add a Menu to the Primary Navigation for your 2 x links.
Add a Menu to your Off Canvas and set it to display on Desktop Only.
In Customizer > Layout > Primary Navigation –> set the Mobile Menu Breakpoint to 0
That should keep the desktop primary nav and the off canvas toggle in view all the time.