If you are using the inifile.fp tool that comes with CVI, no, there isn't a built-in way with these functions to add new lines to the file. You could either do this in post processing of the file with the normal CVI File I/O functions, or you could edit the inifile.fp tool (the source code is provided for you) to add functionality to it to add new lines.
Best Regards,
Chris Matthews
National Instruments