...There's a section to allow you to create a QR with some cmd code to simplify the unlock and even delete a file. You can keep concatenating with &&. The screenshots section should show you everything you need to start using it.
Crucially, this does not use any web api calls. It can run offline.
I'm not a coder so this isn't error handled anywhere near as well as it should. Source is in the files section.
Built on QRCoder by Raffael Herrmann, released under MIT license.
https://github.com/codebude/QRCode