I'd like to permanently hide the list all tabs button (which appears at the far right of the tab bar, when there are many tabs opened). I've found an [extension](https://addons.mozilla.org/firefox/addon/permanent-listalltabs/) to permanently show the button, I want the opposite. I've found several apparently outdated articles suggesting adding some CSS to my userChrome.css, however everything that I've tried so far didn't remove the button. Can anybody suggest what to add to my userChrome.css to hide the list all tabs button (FF 45)? And btw, do I have to restart Firefox every time I edit userChrome.css, or there's a way to automatically/manually reload it?

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

#tabbrowser-tabs ~ #alltabs-button {display:none!important;}