That’s actually several different questions, but the one that is critical to your situation is that unfortunately that GE device does not support multi channel association and so it can only see one of the endpoints on the plug, not both. There just isn’t any way around that . The 45600 was designed in 2012, which is a long time ago in terms of Zwave.
The reason things work differently in the mobile app is because the smart things hub is able to handle multi channel devices, so it can see both of the endpoints.
But the GE device doesn’t talk to the hub during normal operations , it communicates with the other Z wave devices that it controls directly. So it can’t take advantage of what the hub sees.
If you use one of the devices which smartthings calls a “button controller,” such as the Aeon minimote, those work by having the handheld remote send a request to the hub which then send it to the plug in module. So they will work the same way that the app does, since they can take advantage of the hub’s knowledge.
Handheld Z wave controllers based on old generation technology, such as the GE handhelds, just can’t do that. They are limited to what the handheld device itself can see, and that unfortunately does not include multi endpoint Devices. By the way, the GE device also cannot be used to control a zigbee or WiFi device, while the button controller style devices can, again because their requests are getting passed through the smartthings hub.