Don't fit exactly in this forum, but I make an utility to convert markers from kdenlive project file to chapters in ogm format (text file), works only with one clip. I made this to use the converted file with MKVToolnix. The utility is only for windows, made with VB.Net. It only looks into the xml kdenlive project file for the clip markers and transform them in the text file. The chapters can be edited (name, time) in the utility too.