Hello,
I created a compound CS NAD83(2011)-UTM16-NAVD88 height that you can import into the reference edit window...
take care to check the TOWGS84 parameters according to latest definition of NGS. Now they are all set to 0.....
be sure to have downloades the latest geoid file into the Agisoft geoids folder (us_noaa_g2018u0.tif)