Tab Saver 2 by Mikhail Vyrtsev

WebExtension to manage your tabs. With this extension you can save tabs in current window and open them later. It tracks tabs in opened windows, so if you save it as session (+ icon on a window block), you can close the window and restore it later.

It is continuation of my TabSaver addon, but it is made simpler and there is no need to always save session when you want to close window. Sessions are tracked automatically.