Broken in 22.0a2 Rated 5 out of 5 stars
Not functioning. Keyboard shortcut not responding, UI button is hidden (and from Customise Toolbar list) and no entry shown in right-click menu.This review is for a previous version of the add-on (0.8.5.1-signed.1-signed).
There was a bug in 0.9.1 which is fixed in 0.9.2. Due to that bug, I removed v0.9.1 and v0.8.5 (which you have now) didn't have support some tags recently required by addons to have to support (or alternatively opt-out) of private browsing.
Best Offline QR Code Generator for Firefox Rated 5 out of 5 stars
Perfect if all you want is client-side QR code generation to send a website to a phone or tablet quickly and privately.
Image saving could be useful but you can always use Print Screen or another image capture method. Alternatively you can generate and save QR Codes by using a Windows software named "XRen QRCode" which is free too.
Image save functionality added in v0.9.1
The latest addon is still up for review. Brave hearts can download it at https://addons.mozilla.org/en-US/firefox/addon/offline-qr-generator/versions/