system.dataset.exportExcel(filename, showHeaders, dataset, [nullsEmpty])
String filename - A suggested filename to save as.
Boolean showHeaders - If true, the spreadsheet will include a header row.
Dataset | List[Dataset] dataset - Either a single dataset, or a list of datasets. When passing a list, each element represents a single sheet in the resulting workbook.
Boolean nullsEmpty - If True, the spreadsheet will leave cells with NULL values empty, instead of allowing Excel to provide a default value like 0. Defaults to False. [optional]
String - The path to the saved file, or None if the action was canceled by the user.