This SOAP API article describes the SubscriptionProductFeatureList complex type that is used to pass complex data to the subscribe() and amend() calls. Each SubscriptionProductFeatureList identifies a list of zero or more SubscriptionProductFeature objects. A SubscriptionProductFeatureList contains zero SubscriptionProductFeature object if the RatePlan has no product feature.
To create features in product catalog and use them in subscriptions and Zuora Quotes, you need to enable the following:
|SubscriptionProductFeature||SubscriptionProductFeature||Optional||Product feature added to the subscription|