When the configuration synchronization feature is enabled, only the configuration of MaxScale is synchronized and the actual runtime state of the objects is left intact. This means that if a server is to be drained or put into maintenance mode, the operation must be done separately on each MaxScale instance. This also includes the creation or deletion of REST API users.
In addition, any externally referred files (e.g. cache filter rules) are not synchronized. This same problem applies for the GUI as well which is currently incapable of creating or modifying them.