I want to ask if this <?php wp_nav_menu( array('theme_location' => 'primary') ); ?> get all the sub-menu automatically? I saw this one of my downloaded theme and it displays all the submenu only using this and css code. I am curious why it display the submenu even though it doesn’t uses walker class for example like this wp_nav_menu( array( 'theme_location' => 'primary', 'depth' => 2, // 1 = no dropdowns, 2 = with dropdowns. 'container' => 'div', 'container_class' => 'collapse navbar-collapse', 'container_id' => 'bs-example-navbar-collapse-1', 'menu_class' => 'navbar-nav mr-auto', 'fallback_cb' => 'WP_Bootstrap_Navwalker::fallback', 'walker' => new WP_Bootstrap_Navwalker(), ) ); with another walker file like this https://github.com/wp-bootstrap/wp-bootstrap-navwalker. I am new to wordpress and I hope someone would enlighten me. Thanks