I'm here to help share ways so you'll be able to track the employees unpaid time off in QuickBooks Desktop (QBDT).
Yes, you can track the employees unpaid time off or the miss days of work by creating an new payroll item, add the miss hours under the Hours column, with zero rate. Though it calculates zero amount, it still adds up to your employees hours of worked.
You can see attached screenshots for additional reference.
To learn more about creating paychecks in QBDT, you may check this article: Create paychecks.
Feel free to add a post/comment below if you have any other payroll concerns, I'll be always here to help you. Wishing you the best!