Yes this is part of a SellingPlanPricingPolicy https://shopify.dev/api/admin/graphql/reference/products-and-collections/sellingplanpricingpolicy
You can create a fixed pricing policy so that a subscription has a fixed discount for the entirety of its lifecycle or a recurring pricing policy that exists for some limited time as defined by the policy. It sounds like you are wanting a fixed pricing policy. You are also able to define different types of discounts with the pricing policy adjustment types. https://shopify.dev/api/admin/graphql/reference/products-and-collections/sellingplanpricingpolicyadj...