If you are using Smart Markers to populate your data, then you can use the smart marker attribute group:normal.
For example,
&=Data.Item(group:normal,skip:1) &=Data.SubItem
will populate the data in a normal group and add 1 extra row after each grouping.
The output will look like as shown in the screenshot. Please see the following code, I have attached the source.xlsx file used in this code and output xlsx file generated by it for your reference.