organize unity inspector with collapsable sections without using classes

so im making a dialogues system using scriptable objects as a dialogue object and making an array of a dialogue line class to store the lines.....however due to me wanting to add many features to this system, this becomes really hard to work with so i want to add a collapsable section in it without adding a class into a class. Headers are not collapsable so they don't seem to help at all....so please help with this...is there a way or is using a class necessary.....also, is there a way that i can make a text file with a particular syntax and import them to convert them into the desired scriptable objects with the desired properties. my game's story is supposed to be very long so any optimization help is appreciated.

Any and all help is appreciated Thanks in advance!