Work task transaction posting with WIP

I have a question related to probably difficult problem. Since the beginning of 2021 for all the work task transaction we’ve been using posting rules based on re-posting functionality 

(final reposting have place when the specific event on work task is met).

This solution is not good because the dates of the reposted vouchers are the same as sourced ones.

Now we need to change the postings using work task cost code, which guarantee that the dates will

correspond with work task finish (I set up such cost code rule together with WIP code).

As we have now  hundreds of tasks (we can not close them now), then:

1. I transfer all the transactions (finished, not transferred yet) using “old” posting rules. This will generate e.g. T1 with WIP accounts (not with WIP cost code)
2. I’ll change the posting rules for the new once (based on the work task cost code with WIP)
3. I need to change the characteristics of the transaction  in unfinished state but already transferred. Here is my problem.

If I finish work task and try to transfer again I have the error  - no value for the account code parts.

I think that I should try somehow (correct me if I’m wrong) “say” to the system that the transaction

which I close (finish) after I’ve changed the posting rules have had defined with the cost code, reversal condition and reversal date rule.

How do I reach that ?

I know that the system has no such functionality but maybe most advanced method (like e.g. SQL procedure) have been used and someone has experience with that.

I trust in your knowledge (have had several help from you, Community),

Mark