Rated 5 out of 5 stars
Thanks, works fine. The inbuilt keyboard shortcut also works, but I like having a button. Agree that a monochrome or even grayscale icon would look less glaring. I used userChrome.css to sub the inbuilt 'Get Messages' icon:
--webextension-toolbar-image-2x: url("chrome://messenger/skin/icons/getmsg.svg") !important;
list-style-image: url("chrome://messenger/skin/icons/getmsg.svg") !important;
Exact css depends on system; YMMV
Version 2.0.2 now offers the possibility to choose between different icons.