I'm trying; when I add multiple .mka's nothing appears. When I add a single one, it looks like a bad windows overlay.
Increase the width of your Chapter Editor tool dialog. This dialog expects only one file and only shows the current chapters (if any) and Default Audio stream of the loaded file. Yiu can change the default audio stream, if there is > 1 audio stream.
To load multiple files use the First MMH tool and drag multiple files onto the grid. You can then change the default audio stream for all.