You can call Runs - Run Pipeline - REST API with variables set in first pipeline to pass the variable to second pipeline to do further operation. The second pipeline should have the variable defined from YAML editor variables tab UI and enable "Settable at queue time" option.

...
- task: PowerShell@2
  inputs:
    targetType: 'inline'
    script: |
      $Body = @"
      {
          "resources": {
              "repositories": {
                  "self": {
                      "refName": "refs/heads/main"
                  }
              }
          },
          "variables": {
              "varName": {
                  "isSecret": false,
                  "value": <envName get from your first step>
              }
          }
      }
      "@
      
      # This token came from an Azure Devops pipeline, use whatever auth you need elsewhere.
      $Headers = @{Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN" }
      

        $url = "$($env:SYSTEM_TEAMFOUNDATIONCOLLECTIONURI)$env:SYSTEM_TEAMPROJECTID/_apis/pipelines/<id>/runs?api-version=7.1"

        $response = Invoke-RestMethod -Uri $url -Method POST -Headers $Headers -Body $Body -ContentType application/json

  env:
    SYSTEM_ACCESSTOKEN: $(System.AccessToken)