I don't know of anything expressly designed for the purpose. I've tried both
the Basic & the Segmented Pyramid in both Word 2007 and Word 2008 on my Mac.
Same success in all cases.
That tells me you're working with a Word 97-2003 file or an RTF in
Compatibility Mode - take a look at the Title Bar. That format doesn't
support the *new* graphics engine which allows the capability. If you save
as a .docx you should be able to insert one of the actual SmartArt Diagrams.
As long as you're dealing with a file format earlier than .docx the
workaround you've discovered is the only way I know of other than text the
same color as the box or covering it with another shape. Neither of the
latter strike me as being preferable
Regards |:>)
Bob Jones
[MVP] Office:Mac