Papyrus question about altering character nodes

[Texdarkstar]

I have researched this for a while now and I still can't figure this out. How do mods like BeeingFemale, SLIF etc modify the characters morph/body proportions/nodes inside a script? What frameworks do they use? I've downloaded a few mods that pull this feat off to try and reverse-engineer the code but it's just pex files. I'm modding for SSE, would absolutely appreciate any help with this, thanks for your time.

[Yinkle]

you could look at my mod

Or at Ousnius's mod

 

Both use racemenu as the framework for morphs and include the source psc files

[Texdarkstar]

Thanks for the quick feedback! I'll be sure to check both of them out.