The -G tab is common to all entities but its content is different according to the entity-type. In the Data Structure editor, the -G Lines tab contains the -GC Lines and -GE Lines sections to create/modify comments and error messages respectively for the current instance.
Click the downward arrow of each section to develop its content. The references and tasks on the different sections of -G tab for a Data Structure are developed via the links to be found at the bottom of this pages.