- by Firefox user 12521645, 4 years agoRated 4 out of 5I found the icon for this add-on missing. no way to add it to the menu bar.
Developer responseposted 4 years agoPlease access it using "View->Sidebar" for now. I've opened an issue here: https://github.com/program-in-chinese/HistoryInThreads_WebExtension/issues/12
Thanks for the support.