You can modify the max current with one for sure
And the others are for voltage setting and max voltage
The max current protects your LED
The dimming of the LED you can do over the voltage setting one
If you put a potentiometer in parallel to the voltage setting one you can control between minimum voltage and voltage where the current limitation kicks in
If you want only control the voltage where the LED starts to shine to max led voltage add a tunable resistor in series with the potentiometer