how is that different from what the import module supports? I don't see the actual problem here.
It would help if you could show how you want to represent that data in your domain model.
If you don't have a good reason to store this data in a single entity you should indeed follow Mike's suggestion.
Attributes: Header / DataColumn1 / DataColumn2.
On Import you would then get 5 objects.
After the import you can still do further processing to bring the data into a different format if needed.
Here is the screenshot of the domain Model.
In your spreadsheet, you have 3 columns. To import this data into Mendix, you will need to create an entity with 3 attributes: Header, Datacolumn1 and Datacolumn2.
Then when you set up an import template for this data, you will map column 0 to attribute Header, column 1 to attribute Datacolumn1 and column 2 to Datacolumn2.
Hope that helps,