I don't know what diacriticals means nor the KEY.

Diacriticals are the funny hats and slippers that some letters put on when visiting foreign lands, e.g., ā (an a with a macron), ă (an a with a breve), ą (an a with a ogonek), and č (a c with a haček). &c, &c.

The Key, I believe is a pronunciation key which maps symbols to sounds in a dictionary.

I, too, am quite lazy, but strive not to be ...

Ceci n'est pas un seing.