Nikon Z 8 Reference Manual page 245

Deleting Selected Pictures
1
Select pictures.
Highlight pictures and press the W (Q) button to select; selected pictures are marked with
a check ( ). To remove the check (
button again.
Repeat until all the desired pictures are selected.
To view the highlighted picture full screen, press and hold the X button.
2
Delete the pictures.
Press J; a confirmation dialog will be displayed.
Highlight [Yes] and press J to delete the selected pictures.
) and deselect the current picture, press the W (Q)
245
Deleting Pictures