This filter is applied to use the payment label of restropress, it is including one parameter.
$payment_labels -> an array of payment post type.
An example of how you can append is below:
function get_payments_labels( $payment_labels ) {
$payment_labels = //array of adding labels.
return $payment_labels;
}
add_filter('rpress_payment_labels', 'get_payments_labels', 10, 1);