https://fixyourandroid.com/how-to/access-android-engineering-mode/
Engineering mode or engmode on android is used to tweak the default settings with help of a hidden menu. This advanced mode on android lets users access the separate settings menu where they can configure and tweak the settings like Boost Smartphone Audio, Customize camera settings, tweak WiFi range and signal, Customize Bluetooth, Change Mac address and other tasks on android.