On iOS, when in the config view of the selected channel, there is no settings icon along the top row to get to the Re-Gain function. Currently using iOS 12.2 but the problem occurred on iOS 12.1.4 as well. I have tried this on the iPad Air, iPad Air 2, and the iPad Pro 10.5.
Mixer Model: Behringer X32
App Version: 1.0 (16)