BEA SWIFT Adapter - Manual (Page 81)

The Section Properties panel in the Header panel shows the properties of the header
block, such as whether it is Repeating and Optional.
The Properties panel shows the properties of a field (shown when a field is selected).
It shows whether the field is Optional and it’s Length. For fields of User Header block
and Trailer, additionally the Tag of the field is shown. The fields cannot be added,
altered or removed for Header and Trailer.