Opening quantity to deliver

When adopting manager for a business which has inventory items it has sold and yet to deliver to the customers, how can this be entered for each of the customer involved? That is as you set up your opening inventory, you have both the ones you owned and the ones yet to be delivered that you have already sold before starting to use manager. How can this be reflected?

It’s not possible to enter opening quantity to deliver (or receive) but I suggest to just create negative delivery notes to customers as a workaround.