References: https://help.tableau.com/current/pro/desktop/en-us/dashboards.htm https://help.tableau.com
/current/pro/desktop/en-us/dashboards_create_layouts.htm https://help.tableau.com/current/pro/desktop/en-us
/dashboards_create_watermarks.htm
To add a draft watermark to a Tableau dashboard, you would use an image object. You can overlay this image across your dashboard, possibly with some transparency, to achieve the watermark effect without interfering with the readability of the dashboard content.