Heh, it is there, but if you just hit that key, it's the mathematical symbol ~.

I tried option-shift-that key and it doesn't do anything, you just get the accent grave without the ability to apply it to another letter. Ya gotta do the option-n for a tilde.

I don't really explore either, but I've done enough transcribing over the years that I've had to learn the French and Spanish diacritical marks, and at least know where to find the currency symbols.