Robert,
The Aberration Inspector function in NINA, (actually in the Hocus Focus plug-in) is a real generational change in how sensor tilt is evaluated and changed.
The old school tools like ASTAP or CCD inspector are single point and difficult to use/interpret. Tilt adjustment becomes increasingly important as sensor size increases. The APS-C and Full Frame sensors are definitely large enough to reward correct sensor tilt in image quality across the frame.
The Aberration Inspector uses the multiple focus points in a normal focusing run to create a very detailed evaluation of the imaging sensor tilt and back focus. If given all the information about your focuser unit (primarily how many microns each step moves) it will give the amount of distance from being flat relative to the imaging circle for each corner of the sensor in or out in focuser encoder steps and in absolute distance (microns). Along with that, the Inspector also determine how from from correct backfocus distance the sensor is in or out.
The first time I used it, I was using the ZWO OEM tilt plate. Since the tilt plate is a three point adjustment vs. a four point measurement in the Inscpector, it takes a bit of trial and error to get a feel for which adjustment to make. I was fortunate that my physical configuration allowed access to the tilt adjustment grub screws on the tilt plate - I've seen some that do not (most in fact).
I need to point out that I did not attempt to make the adjustment until I had watched this video from ASG that covers the process in detail:
https://youtu.be/i950CYNBYrcI was able to determine from subsequent focus runs in the following days, that the ZWO tilt plate appears to flex slightly (measured in microns) once it gets moved from full contact with the face of the camera by the tilt adjustment. For that reason, I went to the ASG website and configured/ordered their Photon Cage (demonstrated in the video)
Welcome to ASG Astronomy, llcThe photon cage is designed to work with the information provided by the Aberration Inspector, so I was able to get the tilt with less than 5 microns in just 3-4 iterations. It isn't necessary to use it for the tilt adjustment with Aberration Inspector, but it does make it easier/faster to accomplish. It is also more robust/rigid than the zwo tilt plate (IMO - YMMV).
Clayton