The "Show Console Messages" property is a part of GUI settings on the System Advanced page. Since a new dashboard was introduced for System Advanced and the GUI properties not presented on the page anymore. So, the most suitable place to put the property is the GUI card on the System General page. It would be nice to handle consolemsg property together with other general settings.

ws.call('system.general.config') => {
  ...
  consolemsg: true
  ...
} 

How it will look like: