all the shocks I dealt with so far had quare notches on the adjuster and on the lock nut - easy to adjust with the correct tool or even a punch

this $#@% shock has segment notches

how do I adjust it, please?

Best way I found was to take the shock off the bike, then with one end of the shock held in a vise, loosen the lock ring and turn the adjusting ring with a pipe wrench.

I helped a friend adjust his on the bike by using a long pry bar to push up on the spring, taking the spring pressure off the rings, then using a punch to turn them, but it is easy to slip and gouge up the bike and was awkward to do.