the Application EUI is for grouping the LoRa devices and its related to the application server and that’s the reason its maintained on connectivity settings.
AppEUI - 64 bit number (in v1.1 “AppEUI is renamed JoinEUI”)
This is the unique ID of the Application server. The AppEUI is also unique and should be obtained from the IEEE. This is the destination of the messages sent by the nodes.
The AppEUI is unique to the Application Server and each Application Server will have its own AppEUI. AppEUI: this key is linked to the Application Server. The AppEUI is usually provided to the end node manufacturers by the solution providers (who “own” the Application Server).
Do not create a unique JoinEUI per device and do not use a random sequence. If an OUI is not available, use all zeros to indicate that a join server is not available.