S T R U C T O R I Z E R - User Guide
Settings > Unframed diagram?

This setting is available via the "Diagram" menu:

Unframed not selected

The setting influences the way the diagram is drawn. Boxed (framed) diagrams are somewhat larger because there is a special box drawn around the inner elements. Non-boxed (unframed) diagrams are reduced in size, obviously.

The heading (and a lower margin for diagrams of type sub or includable) of a non-boxed diagram is gray whereas the box around a boxed diagram is white:

program, boxed  program, un-boxed 
Boxed diagram  Un-boxed diagram 

For further details about this, please look here...

Whether diagrams are presented in boxed (framed) or un-boxed (unframed) style has no impact on execution or code export.