WordPress Menu User Guide – https://codex.wordpress.org/WordPress_Menu_User_Guide
How to Automatically Create WordPress Navigation Menu Items – https://clicknathan.com/web-design/automatically-create-wordpress-navigation-menu-items/
How to Add Custom Navigation Menus in WordPress Themes – https://www.wpbeginner.com/wp-themes/how-to-add-custom-navigation-menus-in-wordpress-3-0-themes/
Flexbox examples – меню – https://vahro.ru/other/flexbox-examples-menyu/
Dropdown menu 3 levels – https://vahro.ru/other/dropdown-menu-3-levels/
Примеры меню – https://vahro.ru/other/primery-menyu/