It took me a while to find where this setting was. I was intially looking under Settings > Websites > Content Blockers and I tried searching the menubar context menu as well (under the Help submenu). So, to anyone wondering where this is actually located: Settings > Privacy > Show Filter Lists.
2 suggestions here:
- Add a blurb that the content blocker can be modified under Privacy. Or just add the same button under the Websites > Content Blockers section
- Change "Show Filter Lists" to something like "Manage Filter Lists..." to make it explicit that it is more than just a place to see the filter lists