In Editing a sales batch invoice, need to add an extra row for an extra sales code

E.g, batch sales invoice €2000 posted with one row to sales code 4000.

I later need to change this to €1500 to code 4000 and €500 to code 4500.

But I cannot add an extra sales code, I can only move all €2000 to a different sales code or leave all €2000 at code 4000.

If this could be added in the next upgrade that would be brilliant as this is something that I regularly need to do, and often it can be months later and the vat etc is done, so I cannot delete and re-input the transaction.

Have just switched from Tas and didn't realise this was the case.

In the meantime, I will need to input any sales invoice where this could potentially happen with two rows ( e.g posting €1,000 to code 4000 twice).