[WooCommerce] Add custom order is paid statuses

functions.php

<?php

add_filter( 'woocommerce_order_is_paid_statuses', 'my_custom_woocommerce_order_is_paid_statuses' );

/**
 * @param array $statuses
 * @return array
 */
function my_custom_woocommerce_order_is_paid_statuses( $statuses ) {
	// already included statuses are processing and completed
	$statuses[] = 'my-custom-status';
	$statuses[] = 'my-other-custom-status';
	return $statuses;
}