Modbus, write register

I have a Wemos D1 programmed in Arduino connected via Modbus RS485. There are seven integer holding registers, five for reading from the D1 and two for writing to it. The reading works fine using the instructions from the sensor section of the documentation.

    - name: r0t
      unique_id: r0t
      scan_interval: 10
      slave: 180
      address: 11
      data_type: uint16
      device_class: temperature
      input_type: holding
      state_class: measurement
      scale: 0.1
      offset: -100
      precision: 1
      unit_of_measurement: "°C"

Now I have three questions:

  1. How do I write to an integer holding register?
  2. Scan interval is set to 10. The five registers are read at a very regular interval of 36 seconds. How come?
  3. While logically a 5 mm bus with 20 m stubs my setup is physically a star configuration. Has anyone got experience on how to terminate that if at all? Terminating all stubs (up to ten in the planned final setup) would create a far too high load, wouldn’t it?

Addendum: I have found

- service: modbus.write_register

As far as I can tell it needs a trigger. The purpose, or at least one purpose, is to display status values on the peripherals. So just like the modbus registers are read every minute or so, I also want to write the current statuses every minute.