Walker class for sub-menu with ACF fields in WordPress
Customizing Tree-Like Data Structures In WordPress With The Walker Class — Smashing Magazine
How to Create a WordPress Custom Menu with Walker Nav Menu Class - Igor Benić
walker - Why is my menu order not working with wp_nav_menu? - WordPress Development Stack Exchange
GitHub - syedabuthahirm/wp-materialize-walker-nav-menu: A custom WordPress nav walker class to implement the materialize navigation style in a custom theme using the WordPress built in menu manager.