Now obviously you can’t do that when MM2 is running, but you can do it through an SSH login to the raspberry pi. You will have to tell it which display to use: DISPLAY=:0 scrot /path/to/file.png.

Because I develop from a remote machine (through SSH), the above command comes in handy because I can drop the file onto a shared folder and access it from my remote system.

Using scrot beats taking a picture of the screen whenever you want to show something on your MM installation.