What model of Gazelle bike do you have? It's possible to buy longer stems or stem extenders for quill or stem risers for threaded stem types, here's a
thread about doing this. In addition to not over extending your brake and shifter cables, Ebikes present an additional consideration of the length of some electrical wiring may affect how tall your stem can be raised. I recently replaced my Breezer quill stem with a taller Ergotec adjustable stem and it's made a big difference in riding comfort.