I can not say anything about IntelliJ, as I haven’t used it in ages and never liked the elixir plugin in particular.
Anyway, if you want to run a script, you typically use a terminal and run elixir my_script.exs or mix run my_script.exs depending on your context.
For mix run there should be a “runner” option in the plugin. If you were so kind posting a screenshot of the runners options, I might be able to guide you through setting it up.
Anyway, if you need to set up environment variables, you probably know. Though as you don’t, you probably do not need them :D.
