Docs request: linking env substitution docs in set_env's docs #3036
Description
What's the problem this feature will solve?
set_env option supports environment variable substitution.
This capability is only mentioned in a separate portion of the docs: Environment variable substitutions with default values.
I only discovered the link thanks to #491.
Describe the solution you'd like
Can we link this substitution section within the set_env section? Also, does it apply to pass_env?