When a customer is creating a support ticket, at least, a suggestion/preferable SEN number and instance's URL should be automatic populated on the corresponding fields on the creation issue screen.
Leaving, as well, the option for the customer to change these values, if it owns more than one product, and also presents a drop-down list of recently used SEN numbers and instance's URLs for easy selection, in case the first suggestion/pre-populated one is not the desired one for the current ticket.

Just like the customer's timezone is automatic populated.