I'm assuming this is probably impossible for the .sf2 format, given the lack of option to do so in FL6, but I've seen it done with .xi instruments (attached an annotated example to give you an idea) and thought it was a pretty neat concept, having an envelope for panning.
PS: I apologize for calling that new UI obnoxious. It was a little aggravating, but that was the wrong choice of words, probably. An option to move around the icons and put in separators like with the old GUI would be much appreciated, however.
Unfortunately, the modulation envelope in a SoundFont can only have pitch or filter cutoff as a destination.
If you have two copies of the same sample, panned hard left and hard right respectively, with different values for the volume envelope, you can create some panning effects that way.
