Thanks @neilh20, I think I needed to run
pio pkg install . Now that I have done that – the libraries do indeed clone then install automatically when I update the .ini file.
I’m still not sure I fully appreciate the power of the .ini file and pio commands…but that will come with time I guess.
Git is a critical part of my daily work-life, and I’ll always try to get everyone I know to use it!