QuickBooks actually handles sick and vacation for salaried employees quite well.
For salaried employees, when set up and use sick and/or vacation salary type items (not Hourly), QuickBooks will automatically split the employee's salary for you. And, then when you record the paycheck it will automatically update the vacation and sick balances, and print them on the pay stub.
For example, if you have a salaried employee who is paid $1000 every week, then by default the paycheck earnings table will look like this:

Then add the Vacation Salary item to the check. QuickBooks will split the salary in half so the total salary is the same, $1000:

Next, based on the assumption that the salaried employee works a standard 8 hours per day (or, at least, that is how much vacation they use per day when they take it), enter the hours for each salary item, based on the number of vacation days. QuickBooks will recalculate the pro-ration based on these hours, and will reduce the Vacation available, in this case from 90 to 82 hours, and that will be printed on the paycheck stub:

