Gossygos The gearwheel icon you refer to it's only for private-space-specific things (i.e. install apps on the private space, cross-profile shared clipboard settings, etc.). If you want to install an alternative keyboard app on the private space you should click there.
But keyboard settings -for both the parent and the nested profile (i.e. private space)- are accessed through the normal settings gearwheel, as Ilgar " pointed out.