Is there any way to get a complete view of all unpaid past due installments?

Certainly, just navigate to the Financial Management → Student Fees section of the system and, directly on the screen, you will be shown all payments that are past due or close to the due date, put in chronological order based on the due date.
In addition, using the filters above the list of payments, you will be able to filter by time period, user and specific course.