I love the posth. variations, especially the one in Dflat.
Totally agree, that's one of the most beautiful parts of any piece that I have ever heard!!! What do you think about including the extra variations, I've played it with them and have recordings with them, however I feel it makes the piece a bit long and the variations in the original order seem to balance each other very well?
Schumann's Symphonic Etudes is a monumental romantic work, which I love very much and have played it quite often. I certainly believe it's a good idea to learn the posth. variations as well. You can play them inbetween the Etudes and I strongly suggest to you to follow the order of Alferd Cortot, that seems to work perfectly from my experience with the audience AND the performer. Very important is to decide how long the pauses between the Etudes will be. Sometimes it is effective to make just a short pause, but in other cases you need to make longer ones, in order to allow the listeners to understand the music better. Also, use the repeats as a "test" for your fantasy to do different things in dynamics, phrasing, pedalling etc Good luck!
The order, which Cortot suggests is the following Thema (Andante) Etüde I Var. posth. I Etüde II Etüde III Etüde IV Etüde V Var. Posth. IV Etüde VI Etüde VII Var. posth. II Var. posth. V Etüde VIII Etüde IX Var. posth. III Etüde X Etüde XI Etüde XII (Finale) I don't know if there is a recording by Cortot, but Arrau uses this order and there is definitely a recording by him. I absolutely agree, that Symphonic Etudes deserve to be played often! Good luck for all your future performances!