Dell DW15 docking station audio output set up with mac I'm using a Dell DW15 docking station with a mac High Sierra and wanted to ask how can I set up the audio output so that when I plug in the audio jack in to the docking station the audio output would go to the device connected to the docking station and when it's unplugged the audio output would go to the mac's built in speakers?

Currently it outputs the audio through the speakers in both scenario's.

If I go to System Preferences -> Sound -> Output
and then choose the docking stations USB output it only outputs audio to the docking station, meaning that there is no sound when the audio jack is unplugged from the docking station.
If I go to System Preferences -> Sound -> Output and then choose the
  docking stations USB output it only outputs audio to the docking
  station, meaning that there is no sound when the audio jack is
  unplugged from the docking station.


This is expected behavior.  USB audio devices don't "report back" that speakers aren't attached.  As far as your Mac is concerned, the audio device (USB dock) is seen and functioning.