Hello @Fractal in order to create a validation workflow for dashboards between users in Quick Sight you will need to use APIs and automation.
At the moment Quick Sight doesn’t support implementing native collaboration/sign off via the console.
Here you can find an article that shows how to create a CI/CD strategy in Quick Sight where you first create your dashboard in development, then it is promoted to a preproduction account for validation and, once validated and approved it is deployed to production for consumption (in this case the owner of the validation receives a notification to perform such validation).
Hope it helps.
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