Spoilers for all of The Owl House!
Here's what I think would have been in a full season 3, based on the montage at the beginning of Thanks to Them and also Willow's scrapbook.
So first things first- I think there would be about 20 episodes in the season, given that the first had 19 and the second 21. Probably six of them would be what was covered in Thanks to Them, For the Future, and Watching and Dreaming. So that leaves us with 14 episodes whose stories had to be told in a couple minute montage. However, that plus the scrapbook can give us a decent idea of what some episodes and main themes of the season would be!
Episode 1: My guess is this would be an episode dedicated entirely to the first 24 hours or so after they got stranded in the human realm. Full of sad moments of everyone missing their families, plus some of Luz and Camilla finally being back together. Introducing Vee to everyone, etc. There would probably be a scene much like the one we got at 1:43 with everyone catching Camilla and Vee up on the events that happened in the demon realm.
Episode 2: I really don't know what order things would go in from here, so form here on out the episode number doesn't really matter, it's just episodes I think would be a part of the season at some point. (I want to number them anyway because it feels more organized or something idk). There would be a coming out episode. For sure. You cannot change my mind on this. It's the first part of the montage, and I love it, it's adorable, and it deserved a full 20 minute episode dedicated to it. I don't think that Luz would be very nervous about coming out, given that this is Dana Terrace making the show and homophobia isn't present in the show, like, ever. I think Luz knows her mom would be okay with her being bi, but want's coming out to be special nonetheless. Honestly, if anything, I think Amity would be the most nervous, given that Luz's mom is about to find out Amity is dating her daughter.
Episode 3: Everyone misses their family and is worried about them. Luz sort of acts as their therapist, maybe? Hunter is sad not because he misses his family, but because he doesn't have family to miss. Maybe this episode is their first attempt (of many) at starting a portal to the demon realm, but it doesn't work.
Episode 4: Thrift store day! Just a lighthearted episode where everyone gets their s3 outfit. Wholesome bonding between everyone.
Episode 5: Hunter haircut scene. Oh boy. 4:37. Hunter's hair is growing longer, he has a panic attack because he looks a bit like Belos now. Grimwalker lore heavy. Willow comes in and gives him a haircut, naturally, just like in the montage.
Episode 6: More attempts to get the portal working. (That's all I got for this one, sorry.)
Epsiode 7: Cute Lumity date at an ice cream shop! It's the best, most slice of life date ever, truly everything you could ask for from the concept. Cute blushing, that thing where you both drink a milkshake at the same time, maybe a kiss?
Okay, that's all I got for now, but I'll finish this later. As you can see, I am mildly (Maybe a little more than mildly) obsessed with this show, so… uh… yeah.