How do I configure slack orb notifications to enable desktop notifications?

How do I configure slack orb notifications to enable desktop notifications?

My desktop notifications look like the screenshot linked below after following the article linked below.

version: 2.1
orbs:
  slack: circleci/slack@4.2.0
workflows:
  version: 2
  build:
    jobs:
      - build:
          context: scope-circleci
  build:
jobs:
  build:
    working_directory: ~/cms
    machine:
      docker_layer_caching: true
    steps:
      - slack/notify:
          event: always
          mentions: '<< pipeline.parameters.slack_user_id >>'
          custom: |
            {
              "blocks": [
                {
                  "type": "section",
                  "fields": [
                    {
                      "type": "mrkdwn",
                      "text": "$SLACK_PARAM_MENTIONS -- your build workflow is complete."
                    }
                  ]
                }
              ]
            }

Could you try the following?

custom: |
  {
    "text": "Workflow complete!"
    "blocks": [
       {
         "type": "section",
         "fields": [
           {
             "type": "mrkdwn",
             "text": "$SLACK_PARAM_MENTIONS -- your build workflow is complete."
           }
         ]
       }
     ]
   }