Hi Gary P13.
In the new portal, every time you wish to add anything new you'll see a drop-down list with all your active subscriptions and the subscriptions you're co-admin. If I am not mistaken, that list is ordered by the subscription creation
date. And by default the first item of that drop-down list will be selected, when adding something new. I also don't think there is a way to set your
favorite subscription.

Best Regards,
Carlos Sardo