New SVGFormat save() function that accepts a Point to start drawing the new chart and a boolean to choose if you want the new chart to be appended into the given fileName or not.
So you'll be able to do this:

try {
  tChart1.getExport().getImage().getSVG().save("E:\\tmp\\testJava1.svg");
  tChart2.getExport().getImage().getSVG().save("E:\\tmp\\testJava1.svg", new Point(tChart2.getX(), 0), true);
} catch (FileNotFoundException ex) {
  Logger.getLogger(ChartJFrame.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
  Logger.getLogger(ChartJFrame.class.getName()).log(Level.SEVERE, null, ex);
}