You can add a new menu item in the WordPress admin sidebar using add_menu_page(). This is useful when you want to show custom content or admin tools. Step 1: Open your theme’s functions.php file or create a custom plugin. Step 2: Add this code:

function register_custom_admin_menu() {
    add_menu_page(
        'Custom Menu',         // Page title
        'Custom Menu',         // Menu label
        'manage_options',      // Capability
        'custom-menu',         // Menu slug
        'render_custom_menu',  // Callback function
        'dashicons-admin-generic', // Icon
        25                     // Position
    );
}
add_action('admin_menu', 'register_custom_admin_menu');

// Callback function to render menu content
function render_custom_menu() {
    echo '<div class="wrap"> '; 
        echo '<h1>Custom Menu</h1> '; 
        echo 'This is your custom admin menu page content.'; 
    echo '</div> '; 
}

  Step 3: Save your file and refresh the WordPress admin dashboard. This will create a new "Custom Menu" option in the sidebar. You can customize the content using the callback function by adding HTML or PHP inside render_custom_menu().