I'm not sure if I can explain it in simpler terms, but I'll try.
Every time you see a character or transition to a different scene with a same character the game calls for the outfit description from that character's images.rpy file, where outfits are described. Every outfit is actually a collection of items overlaid over each other (they include things like facial expressions, piercings, tops, bottoms, heads at various angles, etc) and is listed in a fashion I quoted in my previous message.
There are 3 hats that are in Morgan's image folder, but are not used in any of her outfits (old promo images like her "cover card" that you can find on Andrealphus twitter have her wear her hat) and I want to add one or all of those hats to her existing outfits, which I can't figure out a way to do.
Hopefully I made myself clearer now. Thanks.