Если я правильно понял, Вам нужны 
произвольные типы записей и 
произвольные таксономии.
Код для комментария:
add_action('init', 'register_posttype');
function register_posttype() {
        $labels = array(
            'name' => __('Shortcodes', 'dco-sm'),
            'singular_name' => __('Shortcode', 'dco-sm'),
            'menu_name' => __('Shortcodes', 'dco-sm'),
            'all_items' => __('DCO Shortcodes Menu', 'dco-sm'),
            'add_new' => __('Add New', 'dco-sm'),
            'add_new_item' => __('Add New Shortcode', 'dco-sm'),
            'edit' => __('Edit'),
            'edit_item' => __('Edit Shortcode', 'dco-sm'),
            'new_item' => __('New Shortcode', 'dco-sm'),
            'view' => __('View', 'dco-sm'),
            'view_item' => __('View Shortcode', 'dco-sm'),
            'search_items' => __('Search Shortcode', 'dco-sm'),
            'not_found' => __('No Shortcodes found', 'dco-sm'),
            'not_found_in_trash' => __('No Shortcodes found in Trash', 'dco-sm'),
        );
        $args = array(
            'labels' => $labels,
            'description' => __('Custom post type for DCO Shortcodes Menu', 'dco-sm'),
            'public' => false,
            'show_ui' => true,
            'show_in_rest' => false,
            'has_archive' => false,
            'show_in_menu' => 'myplugin-admin.php',
            'show_in_admin_bar' => false,
            'exclude_from_search' => false,
            'capability_type' => 'post',
            'map_meta_cap' => true,
            'hierarchical' => false,
            'rewrite' => false,
            'query_var' => false,
            'supports' => array('title'),
        );
        register_post_type('dco_shortcode', $args);
    }
function wpdocs_register_my_custom_menu_page() {
    add_menu_page(
        __( 'Custom Menu Title', 'textdomain' ),
        'custom menu',
        'manage_options',
        'myplugin-admin.php',
        '',
        plugins_url( 'myplugin/images/icon.png' ),
        6
    );
}
add_action( 'admin_menu', 'wpdocs_register_my_custom_menu_page' );
Скриншот админки.