"Hello!!!"
Is this "heeeeeeeeeello" or "hellooooooooooooooooooooooooooooooooooooooooooooooooooooo" or "hellooooooooooooo" or "hellllllllllllllllllllllllllllllllo" or "heeeeeeellllllllllooooooooo" etc
No idea, but I assume that there it’s more context. Certain words are used for certain situations so if you use them you already go “!!!” without having to spell it out. That’s also how I assume the anime adaptations figure it out.
@Warmmedown
You already got the answer right here “ー”.
Or the none formal internet/manga way you can write it
is using singular or multiple of “〜” at the end of a word.