The option is there, under menu Settings - Main - Monitored Interfaces - Networks.
The Networks button lets you exclude certain networks from monitoring. For example, if you have NetWorx installed on a laptop and you would like it to monitor traffic in your home network only, you can use this feature. It detects all networks you connect to and identifies them based on the MAC address of the default gateway. You can either monitor all networks that you are roaming in, or specify only certain networks to monitor.