Hi Roberto Verde.

Let me provide you additional insights about using the class tracking feature in QuickBooks Desktop. You have the option to assign a class to Accounts, Items, and Names in QBDT depending on your preferences. Here's how:

1. From the Edit menu, choose Preferences on the drop-down.
2. Select Accounting from the left pane, then choose Company Preferences tab.
3. Under the CLASS section, put a checkmark to Use class tracking for transaction.
4. Check the box beside Assign classes to, and then select on the drop-down menu.
   
5. Click OK.

For more details, you can check out this article: How to use class tracking in QuickBooks. 

You can also read this link on how to filter, sort, or total reports by class in QBDT for reference.

As for upgrading QBDT, you'll have the option to add classes by batch if you're using the QuickBooks Desktop Accountant and QuickBooks Desktop Enterprise Solutions versions.

Feel free to tag me in a comment below if you need anything else.