The Billing Portal Configuration object should be made a "first class citizen" in the Stripe dashboard like the other objects. There should be a page that lists billing portal configurations, and that allow creating configurations, the way you can products or prices or anything else in the dashboard, not just editing the one default configuration.
While there is complete API support for creating billing portal configurations, often creating these configurations is a one-time setup job, and editing them often needs to be done by non-developer personnel (much like adding or editing products). For example, suppose you sell different types of subscriptions (with different levels/products/prices). You would not want to allow customers to switch a movie subscription type to a magazine subscription type via the portal, for example. So, you would create different portal configurations, one allowing choosing between the movie subscriptions and the other between the magazine subscription plans. But you would want to set this up in the dashboard, and just put the IDs of the configurations in your code, not write logic to enumerate all the configurations, check whether the configuration already exists, create it if it doesn't, write update logic every time the marketing manager wants the wording of the byline of the billing portal to change, etc.
Managing your billing portal configurations in code is hard also because, unlike other objects, the portal configuration is one of the few objects without a metadata dictionary, with which one could code a program to find and recognize the right portal configuration.
The API for managing and using the portal configurations is great - we just need the ability to do this in the dashboard as well