Is it correct that I would need to update classes/module/PaymentModule.php to enable {invoice_number} to be used in emails, eg bankwire module?
https://github.com/thirtybees/thirtybees/blob/main/classes/module/PaymentModule.php
And then adding here:
$params = [
'{voucher_amount}' => Tools::displayPrice($voucher->reduction_amount, $this->context->currency, false),
'{voucher_num}' => $voucher->code,
'{firstname}' => $this->context->customer->firstname,
'{lastname}' => $this->context->customer->lastname,
'{id_order}' => $order->reference,
'{order_name}' => $order->getUniqReference(),
];
'{invoice_number}' => $order->invoice_number,