The only proper undo closed tabs we have for Firefox Quantum. Best alternative to "Undo Closed Tabs Button" (https://addons.mozilla.org/en-US/firefox/addon/undo-closed-tabs-button/).

PS: please update the screenshot. This addon now has "forget closed tabs" option. Also please remove the option (or add an option to hide the "Clear History" in the menu. This menu item is unrelated to the function of the addon).