Thank you for your reply, @maxgerhardt. I may have installed PIO using pip some months ago, but am not sure.
I searched my hard drive and found no pio.exe nor platformio.exe. I did find platformio.platformio-ide-2.3.2 under ~\.vscode\extensions. That goes away when I uninstall PIO extension from VSCode, as I would expect, but then after reinstalling the extension, PIO Home still won’t come up.
Also, when I type pip list, PlatformIO is not listed.