When using the screenshot tool and then copying, rather than downloading, you get a notification in the bottom right of the screen every time telling you that the shot has been copied to the clipboard. This is annoying after you've seen it the first few times, and can be dismissed only by manually clicking the close button within the notif, rather than pressing escape or clicking on the wider page.
I can't see any way to disable this even in about:config (not that that's the right place to tackle this).
Show the notification via an alert, so it can be dismissed via enter/escape
Provide a "Don't show this notification" option within the notification