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Dashboards are configured with a visibility, controlling who may render the dashboard and its widgets. Widgets automatically inherit the Dashboard's overall visibility, it is not possible to have a single Dashboard with Widgets configured for different visibilities.
Dashboards made visible to "Unauthenticated Users" are publicly viewable at a URL similar to /registry/co_dashboards/dashboard/3. The URL can be obtained (and the dashboard previewed) by clicking the "Render" button in the index of available dashboards.
Primary CO Dashboard
One Dashboard may be flagged as Primary for the CO, via Configuration > CO Settings > Primary Dashboard. When a Primary Dashboard is configured, it will render at the CO landing page (/registry/co_dashboards/dashboard/co:#). Note that any active CO Person (CO Member) can view this page. If a more restrictive visibility is configured for the Dashboard, the structure of the Dashboard will still render, though the Widgets will throw permissions errors rather than render. In general, if a Dashboard is set as the Primary Dashboard, it should be given CO Member visibility.