Setting Environment Variables in MAMP Pro (Nginx)

How does one set Environment Variables in MAMP Pro when using Nginx?

Existing questions on Stack Overflow focus on an Apache implementation: Setting Environment Variables in MAMP?

These variables need to be retrievable from PHP using \getenv()

My attempted solution is the following:

and in PHP:

<?php

\var_dump( \getenv('DB_DSN') ); 
//outputs 'bool(false)'

from Setting Environment Variables in MAMP Pro (Nginx)