I'd be happy to guide you in adding a stand-down time off in QuickBooks Online (QBO).
To do so, you can simply create a new pay type in your QBO payroll account so the stand-down time off won't be deducted from your employee's Paid Time Off (PTO). Let me guide you on how:
Navigate to the Payroll menu and select Employees.
Then, select the employee you need to add a stand-down time off.
Next, in the Pay types section, select Start or Edit.
Choose the payment types your want to add or edit:
Pay type: for hourly, salary, or commission only.
Common pay types: overtime, holiday pay, bonus, or commission.
Time off pays policies: paid time off like sick or vacation.
Additional pay types: other pay types like tips, reimbursement, allowances, or fringe benefits.
Input the rates for each payment type.
To rename some of the payment types, simply select Edit next to it.