But if you want to set a different node to (0,0,0), determine the "current" location of that node - say, (x,y,z) - and simply enter (-x,-y,-z) for the "default origin".

If you are using plant coordinates and your (0,0,0) is no where in your model, be aware that CAESAR II has a limit on the size of these coordinates - a limit that can be exceeded when using millimeters for length and in a big plant.