fellow neurodivergent art student here, hi! I recently submitted my completed body of work so I hope my experiences can help you out a bit
in my opinion, art is one of the easiest subjects to work into your study routine. there isn't too much content to memorise compared to a subject like legal studies or even english.
since you can't study for section 1 of the written exam, and you get multiple essay questions that you can pick from in Section 2 (meaning that you're basically guaranteed to be safe and you won't have a question that you don't know how to answer), the only knowledge you really need to know is maybe 5-7 artists + a couple of their artworks in detail, and some terminology and references that you'll pick up naturally along the way. studying for theory is the part of art that you should probably integrate into your study routine. i think a couple of hours of theory each week will already put you ahead of your peers, because most students are consumed by the artwork that they don't see how equally important theory is too.
theory already makes up 50% of your art marks, so please don't think that the major work is anything too overwhelmingly huge. when you think about english or legal, you're studying for 100% of your grade. but the major work is only worth half of art.
before term 3 next year, you'll get a good amount of time in class to work on your artwork which will usually be more than enough time for an average major work even if you don't put in extra time outside of school.
because of this, you don't need to set aside too much time in your regular study schedule to fit in your body of work. so you don't need to think too much about it. however it's always good to put more effort in to grab that band 6, so i would say that you should always take your artwork home (if possible) after working on it at school so it's always there if you need to work on it.
if any change in a regular routine is difficult for you, i would suggest scheduling 1-2 hours of major work time each week and just following that throughout the year.
but if you think you're alright with a little bit of flexibility, don't strictly plan when you'll work on your artwork, because sometimes if you're in art block and you force yourself to create, the piece turns out worse than your full potential
whenever you feel sick of your other subjects (e.g. if you planned 3 hours for english but got tired of it/distracted after 2 hours, you could fill in that time by working on your art), or when have a bit of free time you could use it as an opportunity to do your major work. whenever you're taking a break from studying, you could put on some youtube videos/music and relax while doing art.
don't feel too stressed! if you still do, i'll tell you that i procrastinated starting my piece for eight months and did the entire thing over the two-week term break before it was due. i really don't recommend going down the same path as me haha, but it's just proof that it's not a huge scary project that you need to be constantly sacrificing your time for. just make sure you're meeting any assignment/progress submission deadlines and you'll be completely fine