Set symbols, bars and other properties by summary level

Answer:

This is possible!  Default summary bars are set via the Layout tab.  

Here's an example using unique symbols, bars and shading for summary levels 1, 2 and 3:

To change properties by summary level:

1.  On the toolbar's Format tab, choose Gridlines, Shading, Font Sizes by Outline Level.

2. On the Outline Level Properties dialog box, choose the Summary Bar tab.

3. Choose the summary level you want to change (2 in the example below) and choose the symbols and bars for Summary Bars: