MacOS: How can I unlock a system plist file to edit? [trying to get rid of a stray Netskope VPN entry]

I'm trying to get rid of a stray Netskope Client (NSClient1) VPN entry that wouldn't go away. I found its traces only in /Library/Preferences/com.apple.networkextension.plist - this is the system's plist not my users. I'm the only user on the system and have admin privileges. However the file is locked and despite being an admin, I can't edit it. Can someone please help me figure out how do I edit this file (or remove the stray VPN entry)? Steps taken so far: (all result in operation not permitted or I don't have permissions to change) - tried to change permissions (via finder's get info option as well as chmod through the terminal) - tried to copy the file to the desktop, edit it and then replace - contacted Apple support (and they said it's not their problem - quite literally) - contacted Netskope (VPN support) and tried to run their uninstaller but that didn't work either [the VPN entry doesn't get listed when I run sudo networksetup -listallnetworkservices] I'm using macOS Sonoma 14.0