Below is the reusuable workflow where I wish to create a connection string to DB ConnectionString in one step and use it in all other subsequent steps so there is no redundancy of code.

---
name: executescript


on:
  workflow_call:

    inputs:

      DBport:
        description: 'Database Port'
        required: true
        type: string
        default: 27017

    outputs:
      srcprimarydbhost: 
        description: 'Source Primary DB Host'
        value: "mydbhost"
        

jobs:


  Detect_Environment:
    outputs: 
      recenvironments: "tempvalue"

    runs-on:
      group: "ARE-Shared"

    steps:
          

      - name: Standard inventory DB connection string
        id: getdbconnstring
        if: always()
        run: |
          $ServerInstance="MYDBHOSTPRD_DB01,3433"
          $Database="util"
          $SQlUserName="svc-user"
          $SQLPassword="${{ secrets.UTILITY_INV }}"
          $ConnectionString = "Server=$ServerInstance;Database=$Database;User Id=$SQlUserName;Password=$SQLPassword;TrustServerCertificate=True"
          echo "ConnectionString=$ConnectionString" >> "$env:GITHUB_OUTPUT"

      - name: Get data from inventory DB
        id: getsnowappname
        if: always()
        run: |

          $squery = "SELECT TOP 1 * FROM util.[dbo].[tbl_inv] (nolock)"
          Write-Host "Invoke-Sqlcmd -ConnectionString ${{ steps.getdbconnstring.outputs.ConnectionString }} -query $squery"
          $sanList = "Invoke-Sqlcmd -ConnectionString ${{ steps.getdbconnstring.outputs.ConnectionString }} -query $squery"

However, I get the below error:

  shell: C:WindowsSystem32WindowsPowerShellv1.0powershell.EXE -command ". '{0}'"
At D:Git-Runnersselfwindowsrunner_work_temp8f233a3a-0af9-4ece-8a6c-2bec58e5f93b.ps1:16 char:137
+ ... 433;Database=util;User Id=svc-user;***;Tr ...
+                                                                 ~
The ampersand (&) character is not allowed. The & operator is reserved for future use; wrap an ampersand in double 
quotation marks ("&") to pass it as part of a string.
    + CategoryInfo          : ParserError: (:) [], ParseException
    + FullyQualifiedErrorId : AmpersandNotAllowed

Note:

1. The error is misleading in a way that there is no & used in the code but probably beccause the connection object variable cannot persist its state when access via GITHUB OUTPUTS.

2. If I combine both the steps as one then the DB query works fine and it is free of any errors.