It would be nice to have custom attributes for rows and cells so that I can track things behind the scenes such as row identifiers that could be used to update a corresponding rows in a the data base. This id would not be editable by the user. There are many more uses I would like this for and that is just one example.
I would rather not have to create a column in the spreadsheet just for this and then hide it. I find that very clunky.