rpress_order_statuses

This filter is applied to use all available statuses for Orders, it is including one parameter.
$order_statuses -> is containing order status.

An example of how you can append additional information:

function get_order_status( $order_statuses ) {
//it returns all the order statuses.
return $order_statuses;
}
add_filter( 'rpress_order_statuses', 'get_order_status',10,1 );