You mean on the hardif ("Batman Interface") - presumably in the "Device" dropdown, right ? What exactly happens there - can you select the Wifi device but it has no effect (which would be expected ecause this is how things work without LuCI) or is there no item for the Wifi at all or are you unable to save when you enter a Wifi network ? If it is the first case, then please see the helptext at the bottom of that form :
"If you want to assign the batman-adv interface to a Wi-fi mesh then do not select a Device in the Device selector but rather go to the Wireless settings and select this Interface as a network from there."