The coin collection sound is a short sequence, stored in one of the SSARs, which are - as DaneGaming said - hardcoded. You'd usually just replace the SWAV file that is used when the sequence plays, but the coin sound isn't a SWAV file; it's a PSG/8-Bit Instrument. You would have to make the sequence link to another track from the linked SBNK file. But I don't think that's possible yet.