showGridlines property
Sets the grid line visible. True if grid lines are visible. otherwise, False.
Workbook workbook = new Workbook();
Worksheet sheet = workbook.worksheets[0];
sheet.showGridlines = false;
List<int> bytes = workbook.saveAsStream();
File('Gridline.xlsx').writeAsBytes(bytes);
workbook.dispose();
Implementation
bool showGridlines = true;