Screenshot icon disappeared from popup windows
After upgrade Firefox to 88.0, the screenshot icon disappeared from popup windows.
Take a Screenshot has been moved out of the page actions container and has become a standalone toolbar button. You can drag this button in customize mode out of the the Customize palette to the toolbar or overflow area. You can also use the "Ctrl+Shift+S" keyboard shortcut (Windows/Linux) or right-click free space on a webpage.