You cannot do that directly from the command line because the marker is strictly a feature of the GUI. You need to instead specify time or frame-based in and out properties on the XML file argument instead. To understand better, export from a timeline marker in Shotcut, View > Application Log, scroll to the end and see for example:
That’s it! Thanks for the solution and thanks for such a nice piece of Software. I was able to create a Rendering Manager based upon Melt and the MLT-Framework for basic Videos like VODs.
Thats so cool that the MLT-Framework is very simple and basic in the way you need to use it. Thanks