I think you could achieve this via the Advanced Excel module
https://marketplace.mendix.com/link/component/116370
The main reason is that with this module you can write a specific Cell at a time. So you could do this via a microflow such that you first add all the cells for the first table by specifying the row index and the column index and afterwards you could add the second table in the same manner.
Hi Disha,
You have to make a 3 entity with table1 & table2 columns.
When you are exporting the excel copy all tabel1 & table2 data in 3 entity with respective columns.
After exporting done delete all objects of 3 entity at the end.
I hope you like the answer.