When a target table as detail has the same primary key as its source table the Windows GUI automatically hides the grid even when a grid is part of the screen design. The Universal GUI doesn't display the same behavior and always shows the grid even when the data model directly implies there will only ever be maximum one detail record.
I would like to propose an optional setting for the Universal GUI to copy this behavior from its Windows sibling. This would take away the need to comb through all screens and possibly having to redesign many, and allow for an easier transition to the Universal GUI.