I assume that we are talking about voluntary rebooking here (no cancellation or schedule change > 15min).
I don't think you will be able to rebook to April 2023 without rebooking fee; that is also why you see a rebooking fee to be collected when you try to rebook online.
I would wait until shortly before you travel date next month to rebook as it increases your chance of a cancellation or schedule change to your flight, which would completely change the situation; however admittedly not likely less than 1 month before traveling.
Then you rebook as far ahead as possible (with payment of rebooking fee ofc) and hope that you have a cancellation or schedule change > 15min to your new flight, which will allow you to rebook for free. It also means you don't rebook as soon as your desired dates in June 2023 becomes possible, but you wait it out/for a cancellation or sch. change (which is likely this far out).