Add raw value combination

[veista]

Data manipulation in HA is almost impossible, This is necessary to make a nice single graph. If you know a better way, do tell.

[APayerl]

I have combined them using a template sensor like this (extract, could miss something but should be mostly ok.)

{% set today = now() %}
{% set prices = [[0, state_attr('sensor.nordpool_kwh_se3_sek_3_10_0', 'today')], [1, state_attr('sensor.nordpool_kwh_se3_sek_3_10_0', 'tomorrow')]] %}
                       
{%- set ns = namespace(coming = []) -%}
{%- for item in prices -%}
  {%- for price_list in item[1] -%}
    {%- set ns.coming = ns.coming + [price_list] -%}      
  {%- endfor -%}
{%- endfor -%}
            
{{ ns.coming }}

Should at least give you an idea!