I like very simple, one task apps, so nostr-backup shouldn't evolve much more than that.
Feel free to clone the project and add the features you want to it.
Due to browser limitations, you'll have to use this project in a different way: you'll have to run it locally, so you will need to get the code from the repo and open the index.html file with your browser.
Check instructions on the repo README or on the index.html file.
Let me know if it worked for you.