I came across this looking while up some symmetry stuff, it should be a good tutorial/example of using the new Dash script despite the age. (apparently it got added in 2017 but i skipped that release) http://vimeo.com/106496966
Global symmetry is not what i expected. I was hoping it would be similar to Modo where you can create a sphere for example, and see another sphere on the other side? symmetry modeling on an object level would be much faster than at a component level