In case you're mad at yourself for closing your precious window with all the right tabs opened, note that Firefox allows to reopen recently closed windows
I generally have a "home" Firefox window with my most used tabs pinned. Sometimes I close it before another window, so I was frustrated to "lose" it and having to redo my pins. But recently I discovered this feature. Joy!
I think it's ALT + SHIFT + S. That is one thing windows gets right. Though I believe they made a new version that is a bit worse for some reason beyond a this mortal's understanding.
Ctrl+shift+S will do Firefox's screenshots. Windows key + shift + s is the windows snipping tool to take a screenshot of anything (aside from hdcp content like trying to screenshot a Netflix video that's copy protected).