config.json

{
    "plugin_type": "analytics_integration",
    "name": "Google Site Tag Integration",
    "form_schema": [
      {
        "default_value": "",
        "field_type": "text",
        "name": "dimension_name",
        "label": "Custom Dimension Name",
        "options": null
      }
    ],
    "description": "",
    "options": {
      "track_layer_decision": "/*\n * Javascript written in this tab will run every time a user is\n * assigned to an experiment and variation, but before any experiment\n * code runs. This hook is useful for tracking which variations a\n * visitor has been assigned to. Click the help icon for more information.\n */\n\nvar decisionString = optimizely.get('state').getDecisionString({\n  campaignId: campaignId,\n  shouldCleanString: true,\n  maxLength: 255\n});\n\nif(!!decisionString) {\n    optimizely.get('utils').waitUntil(function() {\n      return window.gtag !== undefined\n    }).then(function() {\n        var payload = {};\n        payload[extension['dimension_name']] = decisionString;\n        payload['event_category'] = decisionString;\n        gtag('event', 'Optimizely Experiment', payload);\n    }); \n}\n"
    }
  }