Ebusd add-on: ebusctl write

Third party integrations
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1

my setup:
ebusd addon 24.1.1
ebusd adapter v5 Build: 20230501 (ethernet)

I am able to read values from my heating pump via MQTT but how can I write (change) values?

I added in the ebusd-addon configuration this custom command:
–mqttvar=writecb=true

In the developer tools > events I want to test this code:

service: mqtt.publish
data:
  qos: "1"
  retain: true
  topic: ebusd/21576/status.heatpump
  payload: heating mode

but this will not work, what’s wroing