Consider a GitHub Action composite action, like (snippet only):

runs:
  using: "composite"
  steps:
    - uses: azure/login@v2
      with:
        client-id: ${{ inputs.clientId }}
        tenant-id: ${{ inputs.tenantId }}
        allow-no-subscriptions: true
    - name: Get Token
      id: get-token
      run: |
        token=$(az account get-access-token --scope=${{ inputs.ammaScope }} --query accessToken --output tsv)
        echo "::add-mask::$token"
        echo "token=$token" >> "${GITHUB_OUTPUT}"
      shell: bash

I’m confused about the following:

• Does each step run in a separate Bash shell (shell: bash)? Normally, all steps within a job runs in the same shell. If yes, is this the same shell, as the other steps in the invoking job?
• Is it possible for composite actions to export environment variables (export MY_VAR=MY_VALUE), or can it only communicate with the other steps in the invoking job via outputs?
• How can I get rid of warnings about: “pre execution is not supported for local action from ‘./.github/actions/register-api'”?

I think the following references don’t describe the above. Where can I lookup for technical details of composite actions?

References:

• https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#outputs-for-composite-actions
• https://docs.github.com/en/actions/creating-actions/creating-a-composite-action