It would be really great if there's an option to change the address bar icon to gray because it clashes with Firefox's dark theme. Otherwise, it's a great addon

Works great for me! I use it for when I am browsing on my work PC, and I want to quickly send a link to my phone - this is a pretty easy way to do it without any active syncing of work data to my phone.
I chose this addon in particular because it embedded the QR button to the address bar itself (see the screenshot), and not as a separate button on the right side of the toolbar.