What is this "Network Address" field in this image?

I have a query about XBee-PRO 900HP modules with the DM firmware. The following is a network traffic capture from a site where we use them: https://imgur.com/a/kfLQ0Yj

The “Network Address” field is listed as 0xFFFE. All I can find about that, is the unused 16 bit address field in API mode. Is that an actual value that can be set, or is it a useless legacy field in the API packets? From what I understood, it’s a legacy thing and not used in the DP and DM firmware.

Is there any other way to send messages via mesh network to a specific device where we can control the destination device address? We want to have something we can set, so the 64 bit SH:SL value is not quite what we need.

The 64 bit address on Digi Mesh is the devices MAC address. If you want to use a self signed address, you can use the NI and DN commands.