Lack of docs about on methods /issue with using on method

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Hey :) So I noticed that there are little examples in the documentation regarding before:spec, before:run, after:spec, after:run. I've been looking for a few hours for a way to dump the data generated in before:spec into the spec file (which matches the if).

Does anyone have an idea how to do this (or has documented example)? It generally works for me if I throw in the main exported function, but that doesn't quite do what I want because it only gets called before all the spec files.

This is what I have for now, which is working but it's not 100% what I want:

// plugins/index.js
module.exports = (on config) => {
   // magic
   const myVariable = "Magical value";
   config.env.magical = myVariable;
   return config;
}

// test.spec.js
const niceVariable = Cypress.env("magical") // get "Magical value"

What I need (pseudo code/not working)

module.exports = (on config) => {
   on("before:spec", async ({ relative }) => {
      if (relative === "cypress/integration/test.spec.js") {
         // magic
         const myVariable = "Magical value";
         config.env.magical = myVariable;
      }
   });
   return config;
}

// test.spec.js
const niceVariable = Cypress.env("magical") // get "Magical value" (for now getting undefined)

Edit

Ok, sounds like I can't change envs... at all, so working with task in before?