Creating a new library. Tutorial please

PaulS:

extern SerialPreset SerialPreset;

What do you think that this is doing? It probably is not doing what you think it is.

I have no idea what it should be doing to be honest. I'm brand new on this library stuff but I really want to learn this.

Morse telegraph; // Create in instance
.
.
.
void loop()
{
telegraph.dot();
}

I cant see "telegraph" in the original morse code.
Did you change it?