Note that this isn't a pattern as such, and not a token. ENV_ is a special prefix to a variable name that, as @tiffle says, denotes it should override any regular environment variable with the same name (minus prefix, obvs).
So any variable you name ENV_<whatever> will be available as an environment variable when you "Execute Shell Script", either as an additional variable or overriding an existing one. As @Airy said, you can printenv those to see the "defaults", and it's easy to demo the override:
ENV_ Demo.kmmacros (4.7 KB)
