With two separate navigation section (three, including on page nav) we'll need to come up with a strategy for mobile navigation.
One possibility is to include subpages withing the left sidebar's WP menu. We'd hide the subpages on desktop but make them available via hamburger menu on mobile.
As far as on page navigation, it could be included in a separate area (top of the page) or excluded entirely.
With two separate navigation section (three, including on page nav) we'll need to come up with a strategy for mobile navigation.
One possibility is to include subpages withing the left sidebar's WP menu. We'd hide the subpages on desktop but make them available via hamburger menu on mobile.
As far as on page navigation, it could be included in a separate area (top of the page) or excluded entirely.