We have lessons with 4 week and lessons with 2 week cycle

If in one timetable you have lessons, which are repeated every 4th week and lessons which are every second week, you can use Combine function and schedule lessons as required. Follow these steps:

1. Create 4 weeks timetable at first. Please see: How can I define weeks?
This will ensure, that you can create lessons in 4 weeks cycle

2. Create "AND" combination by selecting required weeks (with holding "Ctrl" key) and then press button "Combine". For 2 weeks cycle:

Combine Week A AND Week C and create Odd Weeks combination.
Combine Week B AND Week D and create Even Weeks combination.

These combinations ensure, that the lesson will be placed in both "odd" weeks (A, C) or in both "even" weeks (B, D).

3. To ensure, that the lessons can be placed either in odd or in even weeks, combine these two new options with OR combination. Again, simply select Odd weeks and Even weeks rows, click "Combine" and use "OR" option.

Now you can specify not just usual options for multiple weeks timetable, but also
1. Lessons which should be placed ONLY in Odd/Even weeks on same positions
2. Lessons which should be placed either in Odd or in Even weeks /so in two 2weeks cycle/