This flow uses the “brightness_move” Zigbee2MQTT commands (just like directly paired bulbs and remotes) for perfectly smooth dimming.

The flow is designed to be used with buttons that sends pressed/released commands or on/off, true/false, 0/1, etc. It does not have to be input from Home Assistant nodes.

Long press (hold): increase or decrease brightness. If the light is off, when the button is held, the light will start from minimum brightness and slowly increase. If the light is on, it will be decreased or increased to the minimum or maximum without turning off.

Short press: toggles the light on and off (select resume brightness level or full brightness by double clicking the subflow – see below)

Download this subflow here: https://flows.nodered.org/flow/b3aa835c9ead60b8ec96b63ae2e80595

I also made a similar flow to be used with deCONZ which can be found here