I found that when I edit the image, usually just cropping, there is a button at the top.
The button is Save. That's the one that overwrites.````````
Butt I found a command in the pull down menu (the 3 dots) has an option to 'Save copy'
which doesn't overwrite.
Since I saw the 'Save' command at the top I never bothered to ;look elsewhere.
I thing they should be switched.