Right now I’m afraid that is not directly supported.
Irregular patterns (ie something that does not follow into a simple pattern like once/twice/three times every 1st/2nd/3rd day/week/month, etc) and varying times per recurring instance are not directly supported.
One partial workaround is to create a pattern that covers all of the target dates and then delete individual instances – but I appreciate that may not be practical in every case.
Beyond that, this is certainly a popular feature request (feel free to upvote it/comment on it to show your own support) and one we definitely want to drive forward, though I can’t give you any sort of timeframe for that just yet.