Labeling and enzymatically modified stevia
In the US, if you use enzymatically modified stevia extracts below a certain threshold, such that they alter your perception of sweetness or enhance sweetness, but are not acting as sweeteners, you can call them ‘natural flavor’ on the label. If you go above that threshold and your enzyme-modified product is functioning as a sweetener, it must be described as enzyme modified steviol glycosides, or some equivalent, and must be generally recognized as safe (GRAS).