你可以用真棒WP_Admin_Bar &；与挂钩admin_bar_menu:

/**
 * Add a "Log out" link directly to the admin bar.
 * 
 * @link    http://wordpress.stackexchange.com/q/141446/1685
 * 
 * @param   WP_Admin_Bar    $wp_admin_bar
 */
function wpse_141446_admin_bar_logout( $wp_admin_bar ) {
    if ( is_user_logged_in() ) {
        $wp_admin_bar->add_menu(
            array(
                \'id\'     => \'my-log-out\',
                \'parent\' => \'top-secondary\',
                \'title\'  => __( \'Log out\' ),
                \'href\'   => wp_logout_url(),
            )
        );
    }
}

add_action( \'admin_bar_menu\', \'wpse_141446_admin_bar_logout\', 100 );