You can create your own variable pay categories to add to employee salaries when needed.
1. Select Payroll tab under Configuration in the navigation panel on the left
2. Scroll down to Variable Pay and click on Add New (example: Profit Sharing)
The default options include Overtime, Bonus and Commission. You can edit those or add to the list as shown above. The options will be visible in both the payroll table and editing individual employee payroll tab when you edit variable pay as shown below.