I figured it out... in case anyone reading this thread is interested in the result:

 

I found that (1) setting the button template explicitly {and not using AutoConfigure} and (2) including G_Start and G_End in the template string to indicate logical groupings of buttons will create button groups that will "wrap" when necessary {after the G_End of a button group} to shrink the Width of the entire control. When the control's Width is enough to accommodate all buttons, then no wrapping occurs.

 

An example of such a template:

 

string strTemp = @"Cut,Copy,Paste,PasteText,Separator,Bold,Italic,Underline,G_Start,FontColor,HighLight,Hr,Separator, Emotion, InsertTable,G_End, ImageGalleryByBrowsing,Link,Unlink,RemoveFormat";

Editor1.Width = System.Web.UI.WebControls.Unit.Pixel(350);

Editor1.Template = strTemp; //button template

 

-Jeff