Nikon D500 - Manual (Page 40)

40 Menu Guide
Choose the primary slot for shooting and playback. Select XQD
card slot to designate the card in the XQD card slot as the
primary card, SD card slot to choose the SD card.
Choose the role played by the primary and secondary cards
when two memory cards are inserted in the camera.
Choose from Overflow (the secondary card is used only when
the primary card is full), Backup (each picture is recorded to
both the primary and secondary card), and RAW primary - JPEG
secondary (as for Backup, except that the NEF/RAW copies of
photos shot at settings of NEF/RAW + JPEG are recorded only to
the primary card and the JPEG copies only to the secondary
card).
Primary Slot Selection
G button
➜ C photo shooting menu
Secondary Slot Function
G button
➜ C photo shooting menu