First open, using an available web browser, the Web GUI of the camera you wish to "rename"
From the left pane of options click the "Information" link
In the "Device ID:" field you will be making your entry as follows...
Example: "Room88 (12X-SDI-G2)"
This will provide you the header of "Room88" within NDI and "12X-SDI-G2" as a sub-selection of the "Room88" header.
Once you have made your desired changes please make sure to click "Apply" followed by a reboot of the camera.
Now you should see you custom name and header show up within NDI.
Note: You can use the same "header" with multiple cameras, using unique "ID"s, to nest multiple cameras under one (1) header.