I had been able to do this, but I can't remember if an Add-on was necessary? I already know that middle-clicking on the refresh
button next to the url address bar copies the current tab along with its history.
I'm asking only about clicking on the tab, not other slower ways like right-clicking on a tab then left-clicking "Duplicate Tab."
D
). I'm pretty sure Duplicate Tab is also a built-in feature having a clickable icon. If you click on customization, I think it is in the collection of feature icons that are available to drag to the toolbar. Then you can just click on the icon to duplicate the tab.