@Yashiki_takajin
If I understand properly, you want the varying column names, and also you want a way where you dont need to use write cell.
One of the method is,
Create an excel file with all the column names that you want in your resultant file.
Keep this file as reference to build a datatable.
Use read range activity to read data from the excel file. Check the ‘Add Headers’ Property.
Now use Add Data Row activity to add all the rows and columns that you are writing using Write cell activity
At the end of complete processing of datatable, use write range activity to write the records into the required excel. (Don’t write into the template defined in step 1)