I tried but no tracks are showed…
Welcome!
Looks like an installation issue (maybe mkmverge was not found?), or your source file is so damaged/incomplete that mkvmerge couldn’t analyze it.
Either way, the program you’re talking about it MKVExtractGUI, a third-party product. This isn’t really on-topic here. Even though it uses MKVToolNix behind the scenes, I cannot really support MKVExtractGUI itself as I’m not its author. My thoughts above are just guesses.