OK, good news: problem is gone. I decided to play around with the mount statement. There's lots of info available, and after a few tries I found one that actually mounts the shared folder and allows me to write to the file from Node-Red.
This is the version that works:
//10.0.0.104/Documents/Raspberry /home/pi/myNAS/myShare cifs username=pi,password=[myPassword],uid=pi 0 0
I've learned a lot of this issue. Colin: thank you for all your patience and help....