Nikon D6 Reference Manual page 784

Playback Folder
Choose a folder for playback.
Option
(Folder name)
[All]
[Current]
732 D The Playback Menu: Managing Images
Pictures in all folders with the selected name will be
visible during playback. Folders can be renamed
using the [Storage folder] > [Rename] option in
the photo shooting menu.
Pictures in all folders will be visible during playback.
Only pictures in the current folder will be visible
during playback.
G button U D playback menu
Description