Hi I figured it, thanks.
For some reason the pop-up was blocked in Chrome but worked in Firefox.
In case anyone else was wondering...
System > Subsystem > MX-One (link) > opens pop-up > Telephony > Groups > Hunt Group (in sidebar)
System > Subsystem > MX-One (link) > opens new pop-up > Telephony > Extensions > Common Abbreviated Number (in sidebar)
Thanks.