I think "preferences" refers to the addon manager. The Addons Manager is there to do just that. If you want to add and remove sites from this add-on so often that you need buttons and context menus, I think your usage is insane. That's not how this addon is supposed to be used. I don't want to add seldom-used context menus and buttons just for that, because they're annoying. Better to uninstall it and use another addon.