There are quite a lot of option to set the recurrence of a task, but not one that offers exceptions.

I want to set a task that would be done weekly but on the 3rd Friday for example (there is then a task that is settle for this moment, every 3rd Friday).

Or then being able to select several possibility (like for days) : on 1st, 2nd, 4th and potentially last Friday of the week

Managing reccuring event in Google Calendar is really easy to change also for a specific event. That would be great if it was as easy in CU. Right now it is a lot of work and I sometime wonder if it is worth it as a tiny exceptionnal change isn't possible.