This fields allows you to override ZAP configuration.
You just have to type key in the first field and value in the second field.
Configuration keys should be specified in the first field using the dot notation based their location in the XML of the configuration file
(e.g "api.key", "connection.timeoutInSecs").
See <a href="https://code.google.com/p/zaproxy/wiki/HelpCmdline">here</a> for more details.