Mario Kart DS Course Modifier is a program for general purpose Mario Kart DS race editing. It has features such as exporting NSBMD + NSBTX, KCL, NCGR + NCLR, and was developed by Gericom until 2014. The program is being obsoleted in favor of better options, such as Mario Kart Toolbox. Download
Mario Kart DS Course Modifier can be downloaded from https://www.romhacking.net/utilities/1285/.