I added a device with name "Switch" and IP address "192.168.1.1".
The Dude only displays the device name (Switch) by default.
I want it to show the IP address at the same time in next line, for example:
Switch
192.168.1.1
How should I config The Dude?
Thanks!

In the "appearance" you can specify any additional information you would like displayed. Since the appearance is able to be set globally, on a sub map or on an individual device you need to determine where is best for your setup.

On the appearance you can put [Device.FirstAddress] in the label... this will continuously display the address.

Lebowski