1. We have a free shipping rule For example, when customer purchase a like $100+, we will offer free shipping.
2. Supplier is using an old fashion way to provide their updated stock numbers weekly Sometimes customer has made a purchase but turn out the product is already out of stock.
So when customer purchased 2 items and the total amount over $100, then they will enjoy the free shipping. But turn out one of the product has been already sold out, then I will need to remove the product in the order. [Order > Edit order] After I took out the product, the total amount will be less than $100, but the customer can still enjoy the free shipping. There a function call "Add product" that I can manually input items like "shipping". But it is treated as "product" rather than "shipping". If customer has a discount code, the item will also be affected.