What is the Cassandra setting for coordinator timeouts for schema change queries?
According to a Datastax representative, the setting which affects schema changes is request_timeout_in_ms.

It should be noted that these timeout settings are not hard timeouts from the time your client application connects to the coordinator node. If the connection is lost, then the timeout counter restarts. Hence why I was seeing some CREATE TABLE commands taking 12 seconds even though I had request_timeout_in_ms set to 10000ms.