If you have VS Code installed, the JSON configuration for the Windows Terminal won't open in Notepad.
Command prompt & Powershell both have GUI settings editors.
VSCode didn't have a GUI settings editor for quite a while.
Now, I will fully cop to out-dated docs being annoying, particularly when most of the configuration isn't really obvious or self-documenting. But complaining about Microsoft of all people offering highly flexible text-based configurations is hugely ironic to me.