You'll need to calculate the extra date field to show today + 5 days.
Add a custom Date field (Date1)
Customize the field with the following formula:
DateAdd("d", 5, [Current Date])

That will calculate a date 5 calendar days from the current date.

You can then create your filter:

Field: Scheduled finish
Test: is less than
Values: [Date1]

As in the original, you may also want to test if the task is already complete.