Hi there, Marco–thanks for getting in touch!
Good question. You can certainly do custom recurring patterns, but the frequencies are pretty locked in. For example, an event can occur Weekly on Mondays every 3 weeks for six months. However, you can’t change the pattern beyond that once it’s created.
We’ve started working on a more freeform way to create recurring patterns but don’t have a set timeframe for when it will be ready.
In the meantime, I think your best bet is to create a recurring event that repeats weekly on Mondays, then edit/delete the specific instances where they fall outside the pattern. You can edit each event individually once the series has been created, though editing an event will take it out of the series.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff