Custom post type submenu sorted by specific meta_key & meta_value

Meta key or meta value in query parameter doesn’t automatically filter the query by default. So you have to filter the query to restrict results.

add_filter('pre_get_posts', 'restrict_events_by_meta');
function restrict_events_by_meta($q){
    if( 
        $q->is_main_query() 
        && is_admin() 
        && 'event' == $q->get('post_type') 
        && isset( $_GET['meta_key']) 
        && isset( $_GET['meta_value']) 
    ){
        $q->set('meta_key', $_GET['meta_key'] );
        $q->set('meta_value', $_GET['meta_value'] );
        $q->set('orderby', 'meta_key' );
    }
}