Hi Saurabh,
To add comments, first you need to create a record in Comments tab. Then provide a reference to it in other tabs using an ID value from Comments tab.
E.g., Variables.Comment=Comments.ID
Note that a column Comment in Variable tab is not a placeholder for actual comments. It keeps a reference to actual comments in Comments tab.
We recommed to generate Excel specs from define.xml included into a CDISC Define.xml v2.0 package and use that file as an example.
Best Regards,
Sergiy