At the moment, you can add add a suggestion on renewing a subscription, using the RenewSerialAddsSuggestion system preference.

The suggestion is disconnected from the subscription, as we don't store the subscription id. When the suggestion is accepted, a new record is created and there is no connection to the existing one.

We should store the subscriptionid and treat the order as a 'order from subscription', which will give it all the features available for subscription ordering at the moment and form a good connection between the serials and acq modules.