The tree drawn: Preview when it is set, else the tree built from UIConfigDetails, else null.
A tree the host already built with BuildDashboardLayoutPreview, so the saved configuration is not parsed again.
The dashboard's saved configuration (MJ: Dashboards.UIConfigDetails). Not used while Preview is set.
A miniature of a dashboard's saved panel layout: nested boxes sized like the saved rows, columns and panels, each box with its panel's icon and title. It fills its container and renders only phrasing elements, so it can sit inside a button. It is decorative (aria-hidden), so the host must name the dashboard. It draws nothing when there is no panel layout.