Thanks for all the help.
The problem was I had the wrong column type. I used "text, column shown in the tag browser" instead of "comma separated text, like tags, shown in the tag browser"
I actually didn't even notice this and calibre is automatically set at the first one. I checked the first post again by Peter T (thanks for the informative post) but didn't see any instructions about making sure to have the correct column type.
If Peter reads this, it might be helpful to newbies like myself to add this bit.
Thanks again for all your help. I'm off to create shelves.