Level "S" refers to the single letter headings that divide the index entries alphabetically. To enable these headings, select the Alphabetical delimiter check box in the Format area.
Inserts heading information such as heading number or heading contents. Click on the icon to select what information to display.
The next two options are available when theicon is selected.
Select the heading information to include in the index entry.
Enter the maximum number of levels to show of the heading number. For example, select “3” to show up to three levels. If the heading number has fewer than three levels, then the actual number is shown.
Specify the formatting style for the main entries in the alphabetical index. To convert an index entry into a main entry, click in front of the index field in the document and then choose Edit - Index Entry.
Uses the initial letters of the alphabetically arranged index entries as section headings.
Arranges the index entries on the same line, separated by commas.