Norm
Premiere Elements Windows and Mac are essentially the same but there are differences. But, I never heard of generating subclips from the Preview Window as one of them.
So, I knew it had to work for Mac as well as Windows. Based on years digging into the details of these programs, there could be one answer for the difference in go and no go under the circumstances.
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Great job of staying with the troubleshooting suggestions.
Best wishes
ATR