you need to add come customization for this and save the confirmed user inside the record and while validating the delivery order, check whether the sale confirmed user and delivery order validating user is the same, else you can raise warning

Thanks Niyas Raphy, but this not exactly what I like to do. I'd like that the user who creates the delivery order is the same as the user who confirms the sale order. Here, the worflow is wrong since it's always the admin user who creates the delivery order. It should be user1. So in the method where sale order is confirmed, I need to force the user to be the current user.