Nikon Z 8 Reference Manual page 394

Option
[Rear-curtain
M
sync]
[Flash off]
s
D
Studio Strobe Lighting
Rear-curtain sync may not correctly synchronize with studio flash systems.
The flash fires just before the shutter closes, creating the
effect of a stream of light behind moving light sources.
Selecting mode P or A after choosing this option sets
the flash mode to slow sync.
Note that photos may be prone to blurring due to
camera shake at slow shutter speeds.
Use of a tripod is recommended.
The flash does not fire.
394
Description Available in
P, S, A, M
P, S, A, M
Flash Modes