Adding sub-headings to your bundle allow you to organise documents under a sub-heading within a section. Documents under a sub-heading are indented under the sub-heading title on the index.
To add a sub-heading to your section, right-click the section heading and select "Add Sub-Heading".
This adds a sub-section to the top of the section; you can then edit the sub-heading title and move the subheading within the section using the grab handles.
