How can I filter the main page of the dashboard by userID?

It is possible to filter conferences for a particular user, so all the calls that the user has made will be aggregated within the Service Metrics tab. Make the search query using the username you are sending to callstats.io. If you are using userID as an object, you should use the alias-name for searching. Specific details of each conference are accessible via the Conference Details tab.

For more information please see this blogpost.