A couple of updates
The “Changing the font” page of the manual has a helpful looking line with a link
" To change the font when reviewing, please see [here]"
However, (today, 6 June 2021) that link takes to the “Introduction” page. https://docs.ankiweb.net/#/templates/styling
Also, I did find a “User interface size” control at the bottom of:
Tools | Preferences | Basic
It’s getting the job done, but it took me a 40 minutes of web searches and dead ends to stumble across it.
I’d still like to be able to change the card size on the fly like I can my browser.