Check Airman, 'Do the 777 and 787 have Mach trim?'
I don't know.
Assuming that most modern high-speed aircraft will have some stability change with increasing Mach, then this has to be managed somewhere in the control system. Exactly where and how, involves choice of design / operational concept, control law, mechanical engineering, and 'normal' trim in manual flight.
My previous post simplified this under the term FBW; more specifically, it involves the design objective of the control law, depiction of stability to the crew - control inceptors, and followup trim. All of which enable considerable variations on a theme, not least how a particular function is defined, or named, within software.
With an 'old school' view, modern FBW aircraft do not have 'Mach Trim'; the term is best reserved for conventional 'hands-on' aircraft.
And then #9, it is named, but not seen.