The Related Items pane has two views: collapsed and expanded. In the Browser Client, use the tab key or select the arrow in the blue side tab (the View Selector) to toggle between the views.
When the Related Items pane is collapsed, the related items are stacked. Select a related item to see details and select the Related Items link to return to the stacked view. When the Related Items pane is expanded, the related items are shown in a row at the top of the pane.
CSM remembers your View Selector choice and the last related item you viewed from session to session and client to client. The views are persisted per Business Object.
In mobile view, the choices do not persist. This is because the expanded view for mobile layouts covers the Business Object form.
To open a related item in this view, right-click the item to show a contextual menu, where you can select to open the record in a quick view window, go to the record directly in the same window, or open the record in a new application window by pressing Shift and selecting Go to record.