title: Why Don't Parameters work in Azure yml template file
body: <p>azure-pipeline.yml</p>
  <pre><code>trigger:
  - master
  
  parameters:
  - name: config
    displayName: Execution Environment
    type: string
    default: QA
    values:
      - QA
      - PreProd
      - Prod
  pool:
    vmImage: 'windows-latest'
  </code></pre>
  <p>The above works perfectly, so in Azure the Execution Environment parameter is shown when I run the pipeline.</p>
  <p><a href="https://i.stack.imgur.com/6yDrg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6yDrg.png" alt="enter image description here" /></a></p>
  <p>If however I attempt to put the parameters in a template as follows:</p>
  <p>azure-pipeline.yml</p>
  <pre><code>trigger:
  - master
  
  extends:
      template: parameters.yml
     
  pool:
    vmImage: 'windows-latest'
  </code></pre>
  <p>parameters.xml</p>
  <pre><code>parameters:
      - name: config
        displayName: Execution Environment
        type: string
        default: QA
        values:
          - QA
          - PreProd
          - Prod
  </code></pre>
  <p>Then when I run the pipeline the parameter is <strong>not</strong> shown.</p>
  <p><a href="https://i.stack.imgur.com/2Wuhp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2Wuhp.png" alt="enter image description here" /></a></p>
  <p>In summary I'm trying to re-use a parameters.yml in different pipelines but extends: template: does not seem to work even though per this link it should:
  <a href="https://docs.microsoft.com/en-us/azure/devops/pipelines/security/templates?view=azure-devops#set-required-templates" rel="nofollow noreferrer">https://docs.microsoft.com/en-us/azure/devops/pipelines/security/templates?view=azure-devops#set-required-templates</a></p>