Custom button map
How do you assign the custom controls on a Nikon Zf — on a body with no AF-ON button and no joystick?
The f2 desk
All stills assignments happen at Custom Setting f2. The bench: the front Fn button (factory-assigned to white balance), the AE-L/AF-L button, the Playback and DISP buttons, the OK button, both command dials, the video record button, and the lens controls — Lens Fn, Lens Fn2, the Lens Fn ring in both directions, the lens memory set button and the lens control ring. There is no AF-ON button and no sub-selector joystick on this body. Video assignments live separately at g2 Custom controls, which can also assign the shutter-release button.
An AF-ON the body didn't ship with
Assign the AE-L/AF-L button the AF-ON role: that is this body's back-button focus. Assign the front Fn button Cycle AF-area mode (added by firmware 2.00) to move between Wide-area C1, 3D-tracking and Auto-area without leaving the viewfinder. On lenses with the controls, pair Lens Fn2 → Save focus position (hold to store a focus distance) with Lens Fn → Recall focus position (one press returns focus to the stored mark).
No detection button — by design
Subject detection has no assignable role on this body: it is switched in [AF/MF subject detection options] in the shooting menus or via the i menu. There is likewise no Preset focus point role — Save/Recall focus position is the memory system here. Firmware did add a Focus limiter role (3.00) that jumps to Custom Setting a15 [Focus limiter setting], and a Film grain role for the firmware 3.00 [Film grain options].
Make the three assignments in f2, then shoot ten frames using only your thumb for focus. If the Fn doesn't offer Cycle AF-area mode, your firmware predates 2.00 — update it.