You can use this to paste an unsigned nostr event from somewhere else so you don't have to risk leaking your key.

I use it myself sometimes to try other nostr web apps, I don't trust the browser environment to keep my key safe, but with the Nostore extension you can enter a random key and when it needs a signature you can copy poste the unsigned event in the Nostur Signer, it will replace the author and signature of the unsigned event with the one from your Nostur account and then you can publish from there.

It's a bit technical because I initially just made it as a small convenience thing for myself but then put it there in case anyone else finds it useful