The killer feature is that you can extend this with your own macros. E.g. if you want the address bar to recognize "hn " as a prefix keyword, and redirect "hn firefox address bar" to, say, Algolia — you simply create a bookmark with "Keyword": "hn" and "URL": " https://hn.algolia.com/?q=%s " (not actually a URL, don't click on it) – %s indicating where the macro parameter substitutes. Then "hn firefox address bar" ma…
This is Firefox's best kept secret. To this day I cannot fathom anyone willingly switching from Firefox to Chrome/Edge/any other Chromium-based browser. There are so many tiny features that are useful at least to myself, while a minor JavaScript performance advantage isn't something that important in the grand scale of things.
There is an honest but much, much more limited attempt top bring a something similar to Chromium: [2].
[1]: https://addons.mozilla.org/en-US/firefox/addon/tree-style-ta...
[2]: https://chrome.google.com/webstore/detail/tree-style-tab/oic...