Does AppKit have Navigation Bars?

Navigation controllers and their navigation bars are a space-saving measure for use on small screens.

The usual replacement for them on a Mac would be a multiple-window interface (like Finder does it for folders), an NSBrowser (if you want to drill down multiple list levels), an NSOutlineView (if a single list of items can be very wide or horizontal screen space is needed for something else), or a split view (you already see this for Mail.app on iPad, where the top-level list is in the left split, the second level on the right).

NSPathControl also has a mode that lets you show a sort of breadcrumbs bar if that would work for you. You could combine that with an NSToolbar as well to create a UI that presents data in a way more suitable to large screens and environments where multiple applications may be used in windows side-by-side.

If you really, badly need a navigation controller, you’ll either have to write your own, or go trawling GitHub for existing implementations from other developers like you.