I can combine values in the Min/Max function in the helpers, but a subtraction feature would be cool. I needed something like that and built it with node red, however having it in HA natively would be great.
I use subtraction to visualize temperature differentials between rooms and the outside. During summertime, I get a notification the moment the outside temperature is lower than inside, so I can open up the windows in order to cool down the apartment.
