I love this extension so much that I avoided updating to Quantum (with what I now see is an ugly interface) and put up with increasingly frequent freezing in Firefox, but this evening the freezing was happening pretty much every time I clicked on anything, so, in sadness and fury, I had to give in and update.
It was great having tiny cat icons on all my bookmark tabs (Now they are only generic "folder" icons, and I especially liked having the red cats on the upper right, in either the blue or green flavor. They never made it hard to view anything, and that was a big plus. Every day it gave me a lift just to see them in my browser. I would be happy to pay for this extension the way you would for other software, and I will keep hoping that its programmer will have a change of heart. It seems to have something to do with Chrome, too. I have never wanted to use Chrome, but if Red Cats will work in it, that may make it worth switching from FF, which both I and my husband loved and have used for many years. (Going to check on that now.)