Modbus write register to Smart heater

Hello

sorry because I´m new to HA and struggeling a lot because I´m not used to the structure/philosophy of HA it would be great if you can lead me to the right direction.

So I like to implement an EGO Smart Heater RS485 into HA which is connected over an TCP converter.

I already figured out how to read values which ist currently at this status:

 # modbus:
      - name: SmartHeater
        type: tcp
        host: 192.168.178.32  # use the IP address of the mudbusbridge
        port: 502
        sensors:
          - name: "Water Actual Temp"
            scan_interval: 10
            unit_of_measurement: "°C"
            device_class: temperature
            data_type: int16
            slave: 247
            address: 5124
     
          - name: "Water Temp Setpoint Poti"
            scan_interval: 10
            unit_of_measurement: "°C"
            device_class: temperature
            data_type: int16
            slave: 247
            address: 5127
     
          - name: "Water Temp Setpoint Individual"
            scan_interval: 10
            unit_of_measurement: "°C"
            device_class: temperature
            data_type: uint16
            slave: 247
            address: 4619
          
          - name: "Excess electricity for Heater"
            scan_interval: 5
            unit_of_measurement: "W"
            device_class: power
            data_type: int32
            slave: 247
            address: 4865

These values I can access by the entities created from the modbus integration.

But in addition to the sensors I like to write 2 values.

#1 at adress 4864 is an intitalisation value “-1” which should be useful to be written e.g. every 5 minutes

#2 at adress 4865 is the power which should be used by the heater (also read as sensor)

But how do I make this write action available?

Out of the documentation I found and modified for writing -500W like this:

action: modbus.write_register
data:
  address: 4865
  slave: 247
  hub: SmartHeater
  value: [0xFE0C, 0x0000]

But even if this would work, it´s only a one-shot and not availabe for adjustments?

So is it the better/right way to use unter “developer tools” the “actions” "write modbus register?

But does this write a long 32-bit register?

Thank you very much in advance!