My late husband LOVED eggplant parmigiana - I never did try to make it for him, the bar was set too high from the way his mother made it - egged and then lightly breaded (from home made bread), and it was labor intensive. The marinara was, of course, home made as well. There was no recipe, of course.
Every time he’d order it when we were out there was always something wrong with it - too heavily breaded, the sauce wasn’t right, wasn’t layered correctly, etc.
My daughter is a wonderful cook and I’m trying to talk her into making it for us - she read over some recipes and said it mostly takes all day so she’d have to set aside a lot of time.
Those old Italian cooks, like my MIL, absolutely lived to cook, the more people over to eat, the better. For them, cooking and feeding people was love.
I cheat a little. My kids went to HS with a big Italian family who owned their own grocery and meat market. They started bottling their marinara sauce a zillion years ago. So I buy the jars by the case, and use that for my marinara. Cheating for sure, but I don’t have to “doctor” it up at all.
I also flour, egg, then dip in Italian style bread crumbs, and pan fry them. Then layer in the baking dish with the marinara and mozzarella. It IS a several hour affair, and best to do it in steps. Which speaking of, it’s time to get these in the pan!
One thing you can share with your daughter: I have, on occasion, done the eggplant slices the day before and assembled them with the marinara and cheese, and then refrigerated overnight. Then I baked it the next day and it came out just fine!