Changing MacOS's IP Address While Booted Off Another Drive
Network configuration information is stored in

/Library/Preferences/SystemConfiguration/preferences.plist


To change the manual IP address assignment, change the string value at

NetworkServices:GUID:IPv4:Addresses:0

To find the right GUID, see the UserDefinedName value for each service.

If ConfigMethod is set to DCHP, the Addresses array is ignored. See the screenshot below for an example of DCHP configuration (Wi-Fi) vs manual (LAN).