Dear Pat,
Thanks for your detailed updates and screenshots.
I do a test again and I'm afraid that you may use long query instead of substringof. Sorry for the inconvenience, substringof may only work with the format substringof('field value', filed name).
I understand that the query you mentioned here is a good idea. Currently I kindly suggest you submit the feedback on the Power Automate UserVoice platform to let our product developers know your requirements and ideas for product improvements. I hope that the query you mentioned here will be soon supported in Power Automate. If our product developers have some updates on the feedback you submitted, they will post updates there directly.
Thanks for your understanding and have a nice day!
Cliff