I am familiar with Linux, I followed your process fine.
Ultimately, I need a scripted, online, solution but that wasn't clear in the op.
With the explanations over in this thread: [HOWTO] Resizing root partition on x86 (March 2023 edition) - #4 by NC1
I was able to use your process online as well, and it works fine. I might try to script it.
I'm still working out why the script from the wiki doesn't work. I was able to plug in a monitor to see the boot, and it hangs at "waiting for root partition at /dev/mmcblk0..." on the first reboot after running the script provided in the wiki.