I've completed this with an Arduino esp32 board.
Wrote a small applet which presents a rest (http) endpoint for "level" command.
This takes a parameter (percentage)
On Hubitat , I wrote a small device driver with "level" ability.
So the device on hubitat takes the command from Alexa with level parameter and sends it to the endpoint on esp32 board.
Then the esp unlocks the step motor (there is a NC relay to prevent unwanted movement)
then enables the motor driver and starts turning the motor.
All is working fine.
Of course I had to make several 3D designs to have fine movement with 3 cups of coffee. Stabilized motor , preferably attached to the coffee machine tray , is very important. And the height of the attachement is also very important.
Having a 3D printer makes things easier.
NOW;
to make it a real zigbee device, I need an Arduino board with zigbee support.
I see that Espressif has a ESP32-H2 chip with zigbee, but could not find a board yet.
is there any zigbee-Arduino solution ?
I really prefer using Zigbee instead of Wifi...
