Environmental Variables

Environmental variables (EV) have powershell variables automatically assigned to them.

E.g.

The EV  ALLUSERPROFILE also has a powershell variable $env:ALLUSERPROFILE  and so on.

https://www.itprotoday.com/powershell/powershell-one-liner-creating-and-modifying-environment-variable

To set or update a machine environmental variable

[Environment]::SetEnvironmentVariable("TestVariableName", "My Value", "Machine")