Combining item data in label card

I’m trying to build a temperature overview page (currently by just using oh-label-cards) with a trend line which is quite ok.
I’ve got one practical issue though because some of my rooms have multiple temperature sensors where none of them is located “perfectly”. Typically I have it in smoke sensors on the ceiling (or close to) which show a relatively high temperature and the other are in radiator valves and therefore below a window AND affected by the radiator.
Therefore my idea was just to get the average temperature between both and show that one just like the location card does it apparently by default. I found no way to achieve it though.
Is this possible?

I guess there is away by creating an AVG group but if there is a UI only possibility I would prefer that.

Yes, there is a way to do it just in the UI, but to be honest, there’s no disadvantage to just using an AVG group. It’s more flexible, easier to maintain if you change the number of sensors, unit aware if you do it right, etc. This is certainly how I do it.

That said, if you want an oh-label-card to show something other than the state of the item it is linked to, then you just use the label property. In that label property you will have an expression that converts the two state strings to numbers and takes the average:

- component: oh-label-card
    label: =(Number.parseFloat(items.Sensor_MasterCloset_Temperature.state) + Number.parseFloat(items.Sensor_MasterBedroom_Temperature.state)) / 2

One additional quirk is a custom .persist config will need to be created because it won’t persist Group Items, even if they have an aggregation function, by default.