Hello! My name is Hallie, and I’m an APM on the CXM team here at HubSpot. I’m happy to share that you can now manually create Subscriptions, as well as import subscriptions! These features are part of an update to additional features the Subscription tool now has. You can read more about these updates in this product update. 
To enable this feature, go to Settings > Objects > Subscriptions and toggle on the “Invoic Creation” Setting, as seen here:
