Actually, I think if you try, '{STATE_ENV:textValueOrTokenNotAVariable}', it will resolve to the process environment variable (not documented).
I started adding it, but there are actually environment variables that apply to proccess/user/machine. I may split it up into 3 tokens: {STATE_ENVPROCESS:textValueOrTokenNotAVariable}, {STATE_ENVUSER:textValueOrTokenNotAVariable}, {STATE_ENVMACHINE:textValueOrTokenNotAVariable}
if needed.