If you want to add discounts for a customer, you can add them as a percentage on the Customer card.
When a SO is created for a customer who has a discount set up, Katana automatically applies the discount rate to each new line item added to the sales order.
If, at some point, you decide to change a customer discount rate, this won't affect any existing sales order line items on Open sales orders. For example, if a customer discount is changed from 10% to 20%, existing line items on an Open SO will stay at 10% while new line items will receive a 20% discount.
Customer discounts are not automatically applied to SOs imported from an e-commerce platform like Shopify. See this article to learn how discounts are applied to imported SOs from an e-commerce platform.