As you can see I keep an eye on the competition regarding visualizers :-)
The simplest way to start the eXo visualizer is to click on the visualization icon:
You can also select "Turn Visualizer On" in the Visualizer menu.
Or use the keyboard command : command-T to start it.
command-T is very usefull when you are writing scripts because using it twice to close and re-open eXo will reload the script from disk.