After learning how to add / delete build project configurations from a Visual Studio add-in, the counterpart to do the same with project platforms:

HOWTO: Add / delete build project platforms from a Visual Studio add-in
http://www.mztools.com/articles/2013/MZ2013011.aspx

This article completes the creation / deletion of solution configurations, solution platforms, project configurations and project platforms. In the next articles I will show how to change programmatically the project configuration/platform for a given solution configuration/platform, along with some issues doing it.