New to OpenHAB rules

Welcome to the forum! I’m not familiar with Loxone. What is the name of the Item that has the temperature value that you want to send, and what is the name of the other Item that you want to update with the temperature value? You may not need to use a rule for this. If you do, I recommend not using the rules DSL, but the new rule engine, scripted automation, Jython and the helper libraries.