create a mega menu with 3 columns and heading of each column will be Title 1, Title 2, Title 3

					<?php


namespace WPTurbo;

function wpturbo_register_mega_menu() {
    register_nav_menus( [
        'mega_menu' => __( 'Mega Menu', 'wpturbo' ),
    ] );
}
add_action( 'after_setup_theme', 'WPTurbowpturbo_register_mega_menu' );

function wpturbo_mega_menu() {
    $menu_items = wp_nav_menu( [
        'theme_location' => 'mega_menu',
        'items_wrap' => '%3$s',
        'echo' => false,
    ] );

    if ( ! empty( $menu_items ) ) {
        echo '<div class="mega-menu">';
        echo '<div class="column">';
        echo '<h3>Title 1</h3>';
        echo $menu_items; // This will output your menu items under Title 1
        echo '</div>';
        echo '<div class="column">';
        echo '<h3>Title 2</h3>';
        echo $menu_items; // This will output your menu items under Title 2
        echo '</div>';
        echo '<div class="column">';
        echo '<h3>Title 3</h3>';
        echo $menu_items; // This will output your menu items under Title 3
        echo '</div>';
        echo '</div>';
    }
}
add_action( 'wp_footer', 'WPTurbowpturbo_mega_menu' );