Expanded only applies to columns that represent fields that are TObjectField descendants. When a column is expanded, a column appears for each child field of the object field. These child field columns each have a column title and appear under the column title of the parent object field. When Expanded is false, child field values are summarized in a comma-delimited string in the object field's column, and cannot be edited. 

Object fields can also be expanded and contracted at runtime through the UI by clicking on the triangle that appears next to its name in the column title. 

Expandable 

ObjectView