• StructuredSelection is an option for cells that determines whether to allow only complete subexpressions be selected interactively in a typeset cell.
• StructuredSelection is more often set at a global level than at the level of individual cells. It applies only to typeset, i.e., BoxData cells. • With the setting StructuredSelection True, you can only select a complete subexpression in a typeset cell. If you try to extend the selection by pressing , for instance, the selection changes in discrete jumps, moving directly to the next higher subexpression. • With the default setting StructuredSelection False, if you extend the selection by pressing , the selection advances by a single character. • See also: Selectable, DragAndDrop.
True, you can only select a complete subexpression in a typeset cell. If you try to extend the selection by pressing 
, for instance, the selection changes in discrete jumps, moving directly to the next higher subexpression. 