Everybody who routinely takes screenshots on a Mac knows very well the motor memory heaven and hell that are the screenshotting shortcuts: ⌘⇧3 to grab the whole screen, ⌘⇧4 to grab part of it, hold ⌃ ahead of time to put the result in the clipboard, press space at the right moment to select a window, hold ⌥ at a different time to remove a shadow, and so on. (Yes,…