Will this work?
This is what I did:
1. Created an new excel sheet with the below content and joined it with the Superstore data.
2. Created a calculated field to assign the sub-category as shown below:
That was really neat Hari!
Thanks for sharing this. It definitely answers the question. My one additional question (but I am marking yours correct anyways), is if there is now a way to accurately depict column grand totals? It seems those would be thrown off with the addition of this row.