You can force how the MainUI displays your Item in Cells, Lists and Standalone cards.
In your case, your screenshot is for a List, so you can add the following to your metadata:
listWidget="oh-stepper-item"
which would result in your Item configuration looking like:
Number HM5_Set_Temp "Küche Soll-Temp [%.1f °C]" <temperature> (G_Heating_Kue,G_Heating_TargetTemps) ["Setpoint","Temperature" ] {channel="homematic:HM-CC-RT-DN:XX:XX:4#SET_TEMPERATURE", listWidget="oh-stepper-item"}
This should show something similar to the below (with a different label, of course):
A little more detail available in my notes.