procedure TForm1.VirtualStringTree1LoadNode(Sender: TBaseVirtualTree; Node: PVirtualNode; Stream: TStream);
var
  TreeData: PTreeData;
  BinaryReader: TBinaryReader;
begin
  TreeData := Sender.GetNodeData(Node);

  BinaryReader := TBinaryReader.Create(Stream);
  try
    TreeData.Column0 := BinaryReader.ReadString;
    TreeData.Column1 := BinaryReader.ReadString;
    TreeData.Column2 := BinaryReader.ReadString;
  finally
    BinaryReader.Free;
  end;
end;

procedure TForm1.VirtualStringTree1SaveNode(Sender: TBaseVirtualTree; Node: PVirtualNode; Stream: TStream);
var
  TreeData: PTreeData;
  BinaryWriter: TBinaryWriter;
begin
  TreeData := Sender.GetNodeData(Node);

  BinaryWriter := TBinaryWriter.Create(Stream);
  try
    BinaryWriter.Write(TreeData.Column0);
    BinaryWriter.Write(TreeData.Column1);
    BinaryWriter.Write(TreeData.Column2);
  finally
    BinaryWriter.Free;
  end;
end;