"it is not possible to not export the detail rows as extra columns."
I'm not sure what you mean by this, because this is exactly how it does work at the moment.
However, to demonstrate what I require, I have attached a zip file containing two Excel files - one containing the current way it is done, the other containing the proposed method. The proposed method uses the Outline feature to display details rows, but it must be saved in .xls format, not .xml.
Could this be raised as a feature request please?
Associate, .NET Development
Morgan Stanley, UK