According to https://codex.wordpress.org/Class_Reference/WP_Query#Order_.26_Orderby_Parameters you want to specify it similar to the following code example:

    $args = array( 	'orderby' => array( 'title' => 'DESC', 'menu_order' => 'ASC' ) ); $query = new WP_Query( $args );

This is supported from WordPress 4.0.