Click the categories on the right to see the lines. Click them again to hide. Thing 6 is already showing – click that to hide it if you like.
Given how ostensibly simple this looks, it did take me ages (a hint -the file is called lines3i.html, so there’s a whole lines1x and lines2x I’ve binned somewhere before getting a good way through the 3s). The main thing was allowing the user to toggle the lines on and off, and not wanting to, or knowing how to, use the standard html tick box to do it. So standard procedure, I went to Stack Overflow, looked for similar questions, asked one of my own and voila.