How can I define lessons that can be outside teaching block(in the afternoon)?

If you have some subjects that can or has to be in the afternoon you can add this cardrelationship:

Now the selected subjects can for example be on 8th period, while normal teaching ends at 5th period. Without this card relationship the software will never create 3 period gap for the students.

Notes:
- If you want to limit the maximum gap length the children can have, you will need to add next cardrelationship:
Class can have max 2 gaps per day
- you can also modify the timeoff for classes and subjects to pack the timetable into less lessons, maybe in some cases this is easier than by adding that relationship