Nikon Z9 Mirrorless Camera - Manual (Page 611)

611 A Custom Settings: Fine-Tuning Camera Settings
This item is available with compatible lenses only. It controls whether
the lens focus ring can be used for manual focus in autofocus mode.
a14: Manual Focus Ring in AF Mode
G button
U A Custom Settings menu
Option Description
[ ON ]
Autofocus can be over-ridden by rotating the lens focus ring
(autofocus with manual override). The focus ring can be used
for manual focus while the shutter-release button is pressed
halfway. To refocus using autofocus, lift your finger from the
shutter-release button and then press it halfway again.
[ OFF ]
The lens focus ring cannot be used for manual focus in
autofocus mode.