Nikon today released version 5.10 firmware for the Z9 camera. The two big features are (1) the ability to set shutter angle (perversely referenced as Shutter mode) so that motion blur remains the same no matter what the frame rate, and (2) the ability to change the color of Zebra stripes as well as the transparency and position of on-screen brightness displays (histogram, waveforms). Smaller changes impact Hi-res Zoom and other changes related to upcoming PZ lenses.
A number of fixes were done, as well, including two that caused some of the "hung camera" problems when taking bursts of images.
Along with the new Z9 firmware, Nikon also updated NX Mobile Air so that it will directly support Adobe's Frame.io when connected to a Z6III, Z8, or Z9 camera. This feature is not in today's update to version 1.3.2 on iOS; only Android users are currently supported.