I left a suggestion for a timeline, let me explain...

When I'm listening to the jungle, for instance, I would appreciate to have from time to time the sound of a jaguar. Or if I want a stormy day, the noise of a lightning, but not always. Also, the timeline would allow to set up time intervals instead of having the sound play constantly (EDIT: already avalaible in the preset editor). EDIT: Or make the sound run a limited time only, with different parts (beginning, end, etc.). Not asking for a true sound editor, though.