David Rodish, I'd hug you if I could--LOL!
I tried your suggestion and it didn't work. BUT ... it inspired me to go another route, which
—alas!—has solved the riddle.
Here's the workaround ...
When highlighting copy from OneNote, you're provided five options as a next step: CUT, COPY, SELECT ALL and PASTE. It's in the fifth option—SHARE—where the solution is found. After you’ve highlighted whatever it is that you want to transfer,
rather using the COPY or CUT functions, go into the SHARE menu. Here, you'll find icons of all the other apps on your phone, one of which is iMessage.
Click on the iMessage icon, and you’ll see the blank message box come up with the PASTE option. Then—viola!—drop in your text and hit SEND.
That’s it.
While there is more navigation with this process, it’s negligible.
Again, thanks for your response. Now, to the chagrin of my colleagues, I've turned into a Text Message Monster :-)