I tried some soundfonts and in field sound selection of mixer there dont apears any sound. But I reply my suggestion from SF: All special sounds and technik (pizzicato, flageolet, several types of trumpet sordine, ...) are specific for one kind od instrument (or more instrument but theyr effect difers - glisando on violin difers of glisando of harp). Beside instrumet players can invent new sound effect characteristic mainly for their instrument.
My suggestion is: Each instrument can have its own set of sound effects and associated command or mark written in score. The score can be open for adding new effects. The syntesizer reads marks or commands searcher just not too big instrument sound set and plays the effect.