How does Poké mon use modifiers to make captured elves flash?

Just change it from the sav file. Remember to save it after you change it. If there is only one pkm file, you can modify it on the pkm file and then import it into the sav file.

Pkm file is a separate wizard data, which can be extracted from sav file or directly made with modifiers.

Sav file is your archive file, which records all your data, including elf data, holding props and so on.