@sagaofsilence.dev
Please check the attached files：
Detail_Master.zip (62.2 KB)
Are they your excepted result?
We generated result with the following codes:
var wbk1 = new Workbook(dir + "template.xlsx");
WorkbookDesigner d = new WorkbookDesigner();
d.Workbook = wbk1;
d.SetJsonDataSource(null, File.ReadAllText(dir + "ShirtsStyleData.json"));
d.Process();
wbk1.Save(dir + "dest.xlsx");