Firefox 52.3.0 ✦ Complete & Simple

This is a thoughtful request. is an older version (from mid-2017, part of the Firefox 52 ESR cycle). While you can't "add" a new feature to the compiled binary without rebuilding the source code, I can design a practical feature that would have made sense for that specific version , and show you how to approximate it using extensions or about:config tweaks available at the time.