The very clever shift adjustment is released by pushing down on the index tab on the "top".
The lock engages a fine rack that has 1mm detents.

Once pressed down, you simply slide the lens into the desired position and release,
locking in that position.
This quickly becomes intuitive and quick and is much better than a fiddly screw lead adjustment used in many T/S lenses.
There is a mm scale across the "top" of the dovetail, 15mm to each side.