Change Or Add Levels In Table Of. Select Custom table of contents. Click on Table of Contents and select Custom Table of Contents In the popup window select how many levels of heading you wish to include at least two under Show levels then click OK.

Select Insert Table of Contents. And setattr can be used to change levels of factor columns by reference no copy. Four of them are used when creating a table of contents.
For more info see Custom table of contents.
This will not work for ordered factors. If you want more levels you only have to change the levels shown in the table of contents. From the Modify Style dialog choose FormatParagraphIndents and Spacing and set the Outline Level to something other than Body Text. Go to References Table of Contents.