You might want to make environment variables that are shared across all of your tests, you can specify these env vars in the Metlo Config tab on the settings page:
YAML
globalTestEnv:
  - name: CREDENTIALS
    value: ...
  - name: foo
    value: bar
These values can then be accessed in a test like normal environment variables but with global prefix before the name:
YAML
id: 065be84b-818f-4dd0-bb0e-6dc788697060

meta:
  name: /user Test

test:
  - request:
      method: GET
      url: "https://test-user-service.metlo.com/user/{{global.foo}}"
      headers:
        - name: Content-Type
          value: application/json
        - name: x-api-key
          value: "{{global.CREDENTIALS}}"
    assert:
      - resp.status < 300