I am Trying To add a System Variable here using PowerShell:
I have tried both ways using
$env:MyTestVariable = \"My test variable.\"
Run PowerShell as an admin. Don't use this if you are trying to modify something like environmental extensions or environmental paths. No need to run refreshEnv and no need to open a new PowerShell window to see it
$variableNameToAdd = "mytestVariableName"
$variableValueToAdd = "some environmental value to add"
[System.Environment]::SetEnvironmentVariable($variableNameToAdd, $variableValueToAdd, [System.EnvironmentVariableTarget]::Machine)
[System.Environment]::SetEnvironmentVariable($variableNameToAdd, $variableValueToAdd, [System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable($variableNameToAdd, $variableValueToAdd, [System.EnvironmentVariableTarget]::User)