How to join three entities in one message / payload to send via MQTT

Hello together :slight_smile:

I think my problem is easy to solve, as I am toatlly not familiar with programming, I spend hours searching the internet, trying different things/commands etc. but I can’t see through the Matrix… :face_in_clouds:

I have to send a number of entities/values from my Huawei inverter+smartmeter to my openwb wallbox to get it working again. The topics are known, even the entities and the format to be send is clear. As long as the Value comes from just one entity everything is fine.
For example: Here is how I send the PV-power from one inverter to the wallbox.

trigger:
  - platform: state
    entity_id:
      - sensor.wr_10_kw_power
condition: []
action:
  - service: mqtt.publish
    data:
      qos: "0"
      topic: openWB/set/pv/1/get/power
      payload: "{{states('sensor.wr_10_kw_power') | float *-1}}"
mode: single

But now I have to send the currents of every phase, comming from thee entities within just one massage / MQTT Payload to the wallbox. So I have to put them them toghether speerated by comma in square brackets in the right format. This is what the manufacture is expecting here:
“Array with the currents per phase in amperes, with decimal places (float), positive reference, negative feed Example: [1.2,2.3,-2.1]”
What do I have to write for payload?

trigger:
  - platform: state
    entity_id:
      - sensor.phasea_current
      - sensor.phaseb_current
      - sensor.phasec_current
condition: []
action:
  - service: mqtt.publish
    data:
      qos: "0"
      topic: openWB/set/counter/0/get/currents
      payload: **??????**
mode: single

Can you please help me out?
Alex :smiley:

Ok…seems like a tough question after all :face_with_peeking_eye:

Or maybe to much prose from my side? :grimacing:

Ok, all I want to know is how to send three entities in a payload that the values are send like [X.X,Y.Y,Z.Z] Decimal places do not need to be corrected (there can be more than one).