Go to the Activity tab, then click on Screenshots.
On the Screenshots’ page, click on any or a particular screenshot to display the full image.
You can see an icon that resembles dial pad click on that and it will reveal the thumbnails gallery.
As an alternative, you can also push the up arrow key on the keyboard to show the gallery.
You can scroll by either using the left and right arrow keys or by clicking on the desired image using your mouse.
You can exit the gallery by clicking on close [X] on the top right corner of the page or by pushing ESC on the keyboard.