Here is a program that can be used to edit the XML files used to store local codes for the Nintendo DS Action Replay. It can also add new games, codes, or folders to existing files. The current version, 1.1 was released on May 9th 2010. Changes include a bugfix for exporting lists that contain special characters, and the removal of Apply buttons in each view.

Warning: This program is free software. It is has been created WITHOUT permission of anyone behind the DS Action Replay. USE AT YOUR OWN RISK! There is NO support for this FREE program. The author takes no responsibility for problems caused by this program. If your computer starts on fire, it's your fault because you probably poured something on it.

Download - Note: This program requires the Java runtime, you can get it from http://www.java.com/ if you don't already have it installed.
This download is distributed as a compiled JAR file. A Windows EXE version is not being provided for this release because I don't believe it's necessary anymore.
See the Readme file for details about changes made in each release.