Upstream from Soquee River Falls, the Left Fork Soquee River splits into two significant forks: the North Prong and Middle Prong. Both prongs flow through an extremely remote and inhospitable section of the Tray Mountain Wilderness. The Middle Prong of the Left Fork Soquee River has several large waterfalls. I've seen pictures of two notable waterfalls here, but aerial imagery suggests there are others. 

The waterfall described here lies on the southeastern slope of Tray Mountain, along the Middle Prong Left Fork Soquee River, about 0.5 mile downstream from the upper falls. At 100 feet high, this is a spectacular waterfall and among the tallest in the region, hence the Tray Mountain Falls name. It has been referenced as Wonderment Falls in Facebook posts by Greg Ford. 

Unfortunately, reaching this waterfall requires an extremely difficult and long bushwhack through very inhospitable terrain. The "best" route is probably from the Appalachian Trail on Tray Mountain. Downstream lies a vast swath of tornado damage, so access from Soquee River Falls is likely dubious. I have yet to see a picture from the base of this waterfall. 

To learn about more waterfalls in the Helen area, see chapter 6 in Mark Ozboyd's "Waterfalls of Georgia" guidebook.