We can do some change to a view and save as a custom view. Then we can subscribe to both the original view and the custom view, and we can receive subscription mail with different contents. But if you run the REST API to query the subscriptions, you will get two subscriptions with same content properties, which is the ID of the origional view. How to differ them via this response of REST API?
Another question, as the REST API ref document discribed, we can create a subscription to a workbook or a view via REST API, but how can we subscribe to a custom view via REST API? And a more basical question, since the concept of 'custom view' has never been mentioned in the REST API ref document, can we query the custom views via REST API?