Using a variable in an automation?

Configuration
1

I use an ispindel device to report various home brewing parameters to HA using MQTT. I currently have automations in place to turn a fridge and heater on and off depending on the sensor values reported.
If I want a target temp of ~18deg, I set the fridge to come on at 18.2 and off at 17.8… pretty basic stuff.
If I want to change this temperature, I currently have to edit the various automations to change these hard coded values.
I would like to implement a new variable using a slider (target_temp) and build this into the automations so they are dynamic and data driven.

One of the current automations looks like this:

- id: '1645475728120'
  alias: MQTT Brew Fridge on
  description: ''
  trigger:
  - platform: numeric_state
    entity_id: sensor.ispindle_temp
    above: '18'
  condition: []
  action:
  - type: turn_on
    device_id: 96777ee75e042a4db19379491af935ea
    entity_id: switch.1280058070039f10b8b1
    domain: switch
  mode: single

How do I amend the 'above: 18' to be target_temp + 0.2 ?
I don’t think I can use a value template directly here?
Do I need to create another dynamic variable set for the actual values I want to switch on and then use these in the automation? Rather than doing the simple maths in the automation itself?

2

Here is an example if how i’ved used input number to custom trigger an automation…

  trigger:
    - platform: template
      value_template: "{{states('sensor.bom_weather_wind_speed_kt') | float(0) > states('input_number.wind_limit_driveway') | float(0)}}"
3

How about using this instead of automations?

Or if you want heating and cooling:

It will appear as a thermostat you can set in your dashboard:

Screenshot 2022-05-13 at 20-22-23 Overview – Home Assistant

4

The thermostat approach looks very very interesting! Good idea… thanks!