I had some trouble figuring out how to get it to work in Firefox Quantum at first, but after reinstalling it, the extension seems to function nicely. The icon in the top right corner of the screen doesn't do anything (unless I'm not understanding something about its purpose), but that doesn't matter so much to me because I find using the context menu more convenient anyway. This extension is very handy and extremely useful whenever I want to save text on the fly. I've used it extensively in previous versions of Firefox, and I'm glad to see that you have put work into making it available in Quantum.