Thanks Noel.
This worked. I deleted the second note in my homemade tie/slur, then left clicked on the first note, and the second note re-appeared, correctly tied.

I also had to go in and delete the old slur. It was upside down because apparently BiaB assigns middle C to the bass clef, or something.

Here is the corrected video:

https://youtu.be/qW9OnLL9g-c

Unfortunately there seems to be no way on YouTube to replace one video with an updated version. But I can post it on the chromatic harmonica forum I frequent. I don't want to make a big deal of the correction on that forum, because they might think the new version sounded better, or something. I don't really know what to do to make it sound better. I did replaced the melody "vibe" with an acoustic piano midi, then turned the volume down on the melody. I turned it down partly because the midi piano didn't sound right mixed with the real tracks piano. Also because the video is intended to be an accompaniment only. I didn't turn it all the way down, because some people play chromatic harmonica entirely by ear, so I wanted to give a hint of the melody. Basically I have no idea what I doing. crazy