Can an employee choose the type of leave balance to use (leave in the current reporting period or overdue leave) when applying for leave?

No, they cannot. If an employee has leave overdue, the system will always use the overdue leave days in the first place, and the earliest of the leave balances will go first.

Example: An employee has 5 leave days overdue left from 2021, 26 days from 2022 and the current leave for 2023 of 26 days. They apply for 14 days of leave in 2023. The system will take the remaining 5 days from the 2021 balance and 9 days from the 2022 balance. The employee will still have 17 overdue leave days to use.