How to move the arrow position of the dimension using toolkit

Try

extern ProError ProDrawingDimensionMove( ProDrawing    drawing,
                                         ProDimension *dimension,
                                         ProVector     location );
/*
  Purpose: Move the dimension to the specified position in the drawing.
           The position before and after the move can be found by
           ProDimlocationTextGet().

  Input Arguments:
     drawing         - The drawing in which the dimension is displayed.
     dimension       - The dimension.
     location        - 3D vector representing the new dimension position.
*/