Maybe you can use Forget about this site. https://addons.mozilla.org/firefox/addon/forget-about-this-site/ It deletes not only history but also cookies, local storage and download history. I found it today, but it seems that it already existed before I made this add-on. However, there seems it has a bug at the moment. Perhaps this small problem will not be a big deal for you. Read my comment. https://addons.mozilla.org/firefox/addon/delete-history-of-current-page/reviews/1326074/