> You can run "[WindowsFolder]System32\setx.exe" directly. It's not a shell command.

Thank you. I will do.

> For modifying an environment variable, please clone the entire path MSI and use an Environment element to update it. Should be a little simpler than that one, because it's a constant.

How about having both? Shortcut menu is more accessible when user want to enable UTF-8 mode after they install Python. (e.g. they got troubled by UnicodeDecodeError and are adviced to enable UTF-8 mode).

> Alternatively, for this kind of policy option, it might be nice to set up some common registry keys to define it. That is a function I've been thinking about for enabling some security features (such as malware scanning), and it mimics how Windows distributes its own configuration already. That'll take a whole PEP, though, and I doubt I'll get it ready in time for 3.10 given the other stuff I've got going on right now.

Registry is also discussed in the thread, but there are no consensus about adding new way to enable UTF-8 mode.
I conclude that we should promote existing way (i.e. envvar) and get feedback from users.

> So provided we adequately document that the setting may impact other versions of Python besides the one being installed, and it's not enabled by default, I'm okay with an MSI-based addable/removable setting for PYTHONUTF8.