Hi Arun Chitumalla,
According to the description, you want insert into multiple header rows when you insert an table in apps for Office.
As far as I know, the table header only have one row, it is the top row. You can get more detail about list and table in Excel from link below:
OfficeTalk: Working with Lists and Tables
As a workaround, you may consider inser the data as matrix and then you can format the data as you wanted. Also if you want to Excel support muiple header rows for table object, you can submit the feedback from link below:
Submit Feedback - Microsoft Support
Regards & Fei
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