Once an assembly is created, the MDS program won’t let you add divided lites without hitting the “Mull Components” button in the center right Display area of the Project: screen. Once that box is checked, the assembly will have a gray outline and you won’t be able to select it. The individual units will be displayed with their unit number or name and an “M” following it. Select one of the units(so it is highlighted gray) and add the divided lites to it. Repeat for each unit of the assembly that needs a lite cut added. Uncheck the “Mull Components” box when finished.