invoices created by pressing new, cannot be added to sales orders in order to reflect invoice percentage

[Mihai Satmarean]

Create 2 sales orders with product A and B and confirm.
Create a invoice by pressing new
Add products A and B
And validate.

I found no way that I can update the sales orders to reflect the invoiced status.

I would propose to leave enabled the "add" button in Sales->Sales orders-> History and from there to be able to select lines from invoices, (like there are lines to be invoiced, we need a new view with lines from invoices) not entire invoice.

If you need more info please ask.

Thank you.