Reopen a closed window with all its tabs in Microsoft Edge

The same thing just happened to me (I had multiple windows open and accidentally closed one that had several important tabs). In a panic I searched for a way to restore the closed window, and came across this very question. From the other answer and the comments, my heart began to sink. But then I realized that they are outdated!

This is how it works in recent versions of Edge (which are based on Chromium). If you close a window containing more than 1 tab, and if you have yet to open any new tab in any other window, then you can reopen the closed window either by right-clicking on the tab area in any of the remaining open windows, or by using the keyboard shortcut CTRL + SHIFT + T as indicated in the picture below.

You can now do this using the new Microsoft Edge feature that ships with the Creators Update in Windows 10, it's called "Set these tabs aside".

While it's not as easy as simply clicking Exit on Chrome or Firefox you can indeed have many New Browser instances open, reboot and click Tabs You've Set Aside and successfully restore your previous browser state.

Edit:

Now with the Chromium version of Edge out, this issue is now fixed.