If you make website tweaks, opening FTP or full IDEs is slow. I built WEditor—a single PHP file you drop on your web-server. Edit code of web-server files in the left panel and see the live rendered results immediately on the right panel. It works in browser allowing you to test code changes in real time. Everything is just one click away: your work opens instantly, saves automatically, and stays out of your way while you focus. It runs directly in your browser, with no account required. Check out the live demo: https://weditor.pp.ua And I would like to know if you already know or maybe use similar app.
Single file tools like this are handy, but the thing I would think about first is access. A file that can edit every file on the server should sit behind a strong password and ideally an IP allowlist, and be deleted when you are done with the tweak. Does WEditor keep backups before it overwrites a file? That would be the main thing I would look for.