Good Grief .. That Chromebook must be still on some old upgrade.
Now with my latest update I just got. When I click on those two little lines or Not Secure,(whatever happens to be up there that day)
The first thing I see is.

https://www.geocities.ws/bkbrat/SiteSettings.png

Then when I click the sight settings at the bottom I go to the page you are seeing, and it now looks like this below Javascript.

https://www.geocities.ws/bkbrat/SOUND.png

So next I am going to post how you update that thing.