History graph zone (show sensor with zone + or - from reading)

Is there a way to show a zone in a history graph that is +/- a value around a reading without creating template sensors for the those values? I’d like to show something like the statistics max/mean/min but define the value myself.

It would be nice to be able to use template values in the history graph for this like below

- type: history-graph
    templates:
      - "{{ states('sensor.pool_monitor_pool_water_temperature') + myvalue }}"
      - "{{ states('sensor.pool_monitor_pool_water_temperature') - myvalue }}"
    entities:
      - sensor.pool_monitor_pool_water_temperature

Not possible with the standard history-graph.
May be some custom card can do it.