Nikon Z 5 Reference Manual page 228

A
Calendar Playback
During calendar playback, you can delete all photographs taken on a
selected date by highlighting the date in the date list and pressing the
O button.
A
Deleting Copies
If the picture selected in the playback display
when the O button is pressed was recorded
with two memory cards inserted and [Backup]
or [RAW Slot 1 - JPEG Slot 2] selected for [Role
played by card in Slot 2], you will be
prompted to choose whether to delete both
copies or only the copy on the card in the
current slot ( 0 233).
Deleting Pictures
186