As discussed in https://discourse.mozilla.org/t/side-view-privacy-features/29171, the current "Side View" add-on has a big problem: Tracking blockes or other add-ons cannot access the side bar. IMHO, this is really bad, as it is a fundamental privacy issue for such add-ons which basically only load third-party content. So it would be great if add-ons have a way to declare that other WebExtensions can do stuff on their web pages. I imagine it like this: * "Side View" sets a property in their manifest (or so) for their sidebar/popup etc. like "addon_access" = true. * PrivacyBadger, uBlock Origin and other add-ons can use a new permission – or some kind of host permission, whatever – to access these and block trackers, etc. In such a way, everything would stay backwards-compatible.