Nikon Z 8 Reference Manual page 405

Tip: Flash Info
Group flash options can be viewed using the [Flash info] item in
the i menu, which can be added to the menu using Custom Setting
f1 [Customize i menu].
Quick Wireless Control
Select this item to control the relative balance between the remote flash units in groups A and B and
adjust flash output for group C. Output for group C is adjusted manually.
1
C: Select [Quick wireless control] for [Flash control] >
[Remote flash control].
2
C: Highlight [Quick wireless control options] in the [Flash
control] display and press 2.
405
Radio AWL