Hi Markus,
FreeMASTER uses either serial or custom debug connection (JTAG/BDM/...) through a debug probe.
So that USB part is really USB CDC (USB over serial). So if you have intergrated the USB CDC code, this should go throug a virtual COM port on your PC.
So from the FreeMASTER perspective, it would look like a normal serial (COM) port.
Hope this helps,
Erich
PS: there is no picture attached to your question.