Enhancement - Accounting Document from Billing Document - change line items

Hi Experts,

Our client has a requirement to display all line items(as shown in Billing document) along with the tax line in the Accounting document. I can explain it as below:

In VF01 transaction code: enter the delivery number.

Press enter to see the number of line items that will be populated in the Billing document.

Click on save.

Here in the Accounting Doc you'll find only 2 line items, one line item is the consolidation of WRBTR and quatity of all the line items in the Billing Document and the other line item is the tax.

We are required to replace the consolidated line item in the Account Doc with all the actual lines as populated in the Billing Document.

For this we tried various methods:

Searched for a BAPI - couldnt find any which will help in modifying the line items before creation of Account Doc

Checked UserExits - Found one SDVFX008 but it didnt have the table which is sent for population of Accounting doc hence there was no way we could modify any table to get the desired output.

Searched the VF01 Flow in Debugger to check when the Accounting Doc is updated, but it also didnt yield any fruits.

Kindly please guide on a way this can be accomplished. Appreciate the help from you all...