Helpfulsister444,
Sorry but I completely missed your post (#9) on Monday. (I do have an eye doc appointment next week, lol.)
It's on the Flex! That part is exactly as shown in the photo posted by "slonison" (post #10) -- look under the
battery fuse box and you'll see that part! See the yellow outlined part (below):

Tell your dad that he has some more work to do on the Flex, lol.
slonison,
You are the man! Your photo saved the day and now we can delare that the mystery part is no longer a mystery but a cable tray for the Flex battery.
Awesome work, Sir!
If you find yourself in eastern MO, look me up and the beer (or bourbon) is on me.
Mr. Bhp,
Thanks for your post. You are 100% correct. I looked at that photo and thought (incorrectly) that the same part was somewhere on the 2019 Mustang. Doh!
Kev555,
Looks like we are out of work on this thread now that this part has been identified.
Thanks, again, to all of you S197ers who contributed to the great outcome.
Cheers,
Chris