Configure regular expression

We configure the action "Automatically distribute customer payments by processes" to link bank payments to processes. For binding we use an additional process field https://i.imgur.com/6GSurHL.png We encountered a problem - in the payment assignments there is no template by which clients specify the number we need (i.e. we cannot specify a template like "number\s[customorder_key]\s" or something like that). But we know that our searched variable is always a 13-digit continuous number. We checked at https://regex101.com/ - by adding the regular expression "\d{13}" you can find the desired value regardless of what is before or after - https://i.imgur.com/574HIDq.png - but we cannot understand whether it is possible to add to the expression "\d{13}" that this is = our variable [customorder_key] by which we need to search for the process to which to bind the payment. Tell me, is it possible to implement such search logic in a regular expression for linking payments?