See the question and my original answer on StackOverflow

It's not documented IMHO (at least I can't find it anywhere). It's based on the content of a file called convert.dir located in C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE (for Visual Studio 2010). This file may not exist or its size may be 0.

When defined, it contains a list of lines, each line corresponding to a converter. The line format is 5 values separated by the '|' character, like this;

relative path to .vsz|relative icon path|localized name|localized description|priority

As an exemple, in my old Visual Studio 2008 installation, here is the content of Convert.dir:


The .vsz file is a standard Visual Studio wizard file.