I've heard some talk and frustration bouncing around that Scratch on MacOS is incapable of saving the Squeak Image. I have found a solution for this, and I hope this will be helpful for all the Scratch-Hackers that use Macs.
The problem with saving the image is that by default, the Scratch Program folder (where the image saves) is a read-only folder, so you can't save to it. Just change the permissions for the folder and you can save the Image File.
Hope this helps.

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