Thought I'd post this in case anyone else needed the config key value for mouse wheel scroll up/down since the in game control menu doesn't seem to pick up the scroll wheel inputs:
Go to the Input.ini (Path:%LOCALAPPDATA%\Witchfire\Saved\Config\WindowsNoEditor\Input.ini) and chance the "Key=XXXXXX" of the actionmapping you want to "Key=MouseScrollDown" or "Key=MouseScrollUp".
For example I wanted scroll up to select my primary and down for secondary:
ActionMappings=(ActionName="PrimaryWeapon",bShift=False,bCtrl=False,bAlt=False,bCmd=False,Key=MouseScrollUp)
ActionMappings=(ActionName="SecondaryWeapon",bShift=False,bCtrl=False,bAlt=False,bCmd=False,Key=MouseScrollDown)