This is one of the best features of new Firefox for me.
Normally I had to start up gimp, select an option, set few seconds timeout, grap the screenshot, and then edit it to show only the part I wanted.
Screenshot in firefox is aware of the page, you can select the appropriate html tag visually.
Actually I thought they removed it in recent Nighlty and was looking for it, after few days I found it in the triple dot, (just next to the start and pocket icons).
Note that there are a ton of ways to grab screenshots on linux that don't require you to start gimp. (I'm assuming you're using linux since you mentioned gimp; yes I know it runs on other platforms, but those platforms also have other, much easier ways to capture screenshots). On linux workstations I usually have one of those quake-console things so I hit whatever key combination triggers it (on my mac it's double-ctrl, brings down iterm 2 window). From any console you can use the "import" command (part of imagemagick package). This lets you grab the whole screen, a single window, or an arbitrary rectangle. `import foo.png` Gnome has its own screenshot tool, and there are likely dozens of other packages that do the same thing.
Screenshot in firefox is aware of the page, you can select the appropriate html tag visually.
Actually I thought they removed it in recent Nighlty and was looking for it, after few days I found it in the triple dot, (just next to the start and pocket icons).