In Edge Drivers they are handled as components of the main device, which is really the way that both the Zigbee and Zwave third-party protocols envision them. Parent/child being established as multiple devices was a smartthings construct, which is why so few of these devices worked out of the box with the platform.
See the following post and the next response to it:
Groovy is on the way out Smartthings Edge is the replacement - #29 by Chares