OH3: How to display an item value?

I calculate the average temperature of different sensors in a rule and post it there to an item:

In OH2 I displayed Temp_Aussen_Korrigiert with sitemaps.

How can I display the calculated item-value in OH3 UI pages (no sitemaps), since I could only manage to display channel-values from things, but not from items…?

My guess is that you do show channel values by means of LINKED items. Your item Temp_Aussen_Korrigiert is not linked to a channel, however you can visualize it the same way as your other items.

There might be some confusion here then because the only way to show values in MainUI is through Items.

If the Item is part of the semantic model, it will show up in the automatically created tabs of the Overview page (Locations, Equipment, Properties).

If not, you’ll have to add a card to a Page and configure the card to show the Item.

If you just want to see what the Item happens to be at the moment, you can browse/search for the Item under Item Settings. Opening the Items page and it should show the Item’s current state at the top.

Or you can bring up the developer sidebar by typing alt-ahift-d and search for your Item. Hovering over the Item will show the Item’s current state.

You can customize how the Item appears in all of those places by adding “default standalone/list/card widget” metadata to the Item.