Apologies for the confusion. We’re in the process of making updates to our Sandbox experience so I will be sure to pass this feedback on to our team. If you’re looking to update your redirect URL for an existing application then you can access our legacy dashboard here. New “Transfer” applications can be created in the updated dashboard which allows you to set a redirect URL and permissions for your application.
An account id can be found by calling the root of the API using the account access token belonging to the account you wish to lookup the account id for.