Thank you for the plugin it is very nice and just what I needed for displaying bus lines in Aarhus.
For others that might want to use a Station ID that is not in the list you can find nearby stops to your coordinates by using this URL: http://xmlopen.rejseplanen.dk/bin/rest.exe/stopsNearby?coordX=id&coordY=id&maxRadius=1000&maxNumber=30
Example:
GPS coordinates
Latitude: 55.67310756519397
Longitude: 12.565741539001467