@merefield @Lilly Many tx. I needed to add this theme component to my “default” theme. As covered here: adding components to a theme. And it works (noting I had earlier added the wrong screenshot):
A couple of comments about the documentation. The correct location is, I believe: Components ▸ Customise ▸ Themes. And the section on adding to themes (see URL above) sounds somewhat more discretionary than it is. Perhaps this wording would be better: "You will need to explicitly add your theme competent to a theme before it will become operational. That includes the “default” theme.
Thanks to everyone for their interest and time. I also have a small bug report for my next posting.