The control panel is for sending actuations to the devices that have actuator components registered. You can for example turn on/off the LED on your Edison (really basic example).
To do so, your agent should have continuous connection to IoT Cloud (currently the only available protocol for that is MQTT). Agent will listen for actuation messages and forward commands to arduino sketches (or some other applications that listen for such commans). You can find example sketches in https://github.com/enableiot/iotkit-samples/tree/master/arduino
Regarding "Send all valid actions" - you can specify more than 1 action to be performed, e.g. "turn the LED on device X", and "turn the LED off on device Y". Multiple actions (or single action) can be saved as complex command and executed when alert arrives.
I think I meanwhile found this out the hard way by trial&error. Wasn't fully intuitive to me.