Hi Martin,
I'm not sure exactly what you did with 'CollapseList' but I have managed to get it working. I just created a simple script that will collapse the list when 'x' is pressed:
public class DropDownMenuCollapse : MonoBehaviour {
public tk2dUIDropDownMenu ddm;
void Update ()
{
if(Input.GetKey("x"))
{
ddm.CollapseList();
}
}
}
Bear in mind that in tk2dUIDropDownItem, CollapseList is a private function so in order to make it work like in the example you will need to change it to public.
Hope this helps.