Not sure if you've found it yet, but on a 3.6 or 3.7 it is found here.
General Settings
Feature Settings
Nortel IP Terminals
IP trunking
Timers
Direct dial
Set 1-5
CAP/KIM Assignments
Dialing Plan
Access Codes
Park Prefix
External code
Direct Dial Digit
Auto DN
DISA DN
Private Access Code
Local Access Code
National Access Code
Special Access Code
Line Pool Codes
Carrier Codes
Remote Access Packages
Package 00-15
COS passwords
COS 00-99
DN lengths
Received # length
CbC Limits
....
If it's a 4.0, I believe it's under Telephony>Genral Settings..
Hope it works for you.