I don’t know about the 737-max, but on the “classic” -300 and -400, we had a “Control-column mounted Stab Trim cut-out Override” switch. Its function was to enable continued use of the stab trim switches after a stuck or jammed elevator event.
The “Control-column cut-out” was a device to enable the pilot to stop a stab runaway by applying opposite elevator. The system would recognise the opposite input and remove power from the stab motors.
The downside of this system was that in the event of a stuck elevator, the cut-out would prevent the pilot from moving the stab. The “Override” switch was there to disable the system in this event, thus restoring stab control to the pilot, notwithstanding the stuck elevator.
The switch was mounted on the aft pedestal and its function became a favourite question of mine during route checks. Few pilots knew what it was for.
Anyway, I wonder if this system (or its malfunction) may have been a factor in these accidents?