OK, in case anyone was following my little "BB" creaking issue, I finally isolated and solved the problem.

On today's ride, I noticed that it was creaking even while coasting, when I did a "slalom" type maneuver or rocked the bike from side to side. That "proved" it was not the BB. Tough to tell where it was coming from. When I came home, I isolated it to the front end as holding the bars hard and rocking the front end side-to-side caused the creak and it even seemed to feel a little loose in the headset. I was concerned it was the lower headset race/bearings, but I finally figured out it was coming from the front hub. I was concerned it might be the bearings, but remembering that the QR skewer can cause this, I swapped out the existing QR (KCNC Ti) for another old one I had lying around.

Problem solved.

Of course, I put the KCNC QR back on and the problem is also solved. So I can only imagine that somehow the QR lever had loosened up or "skipped" a row of threads.

Mystery solved, mostly. I still don't know why it happened, but if it happens again at least I will be able to hone in on the problem.