Sorry to bump an old thread, but I think I just got this working using the Mitsubishi2MQTT code installed on a Wemos D1 mini clone, connected to CN105, and I hadn’t seen an explicit example of how to do this elsewhere.
Once Nodered is installed you can create an MQTT out node and push the temperature you want (a number or string containing a number) to the topic: mitsubishi2mqtt/xxxxxx/remote_temp/set
where xxxxxx is the name of your heat pump entity.
You can even discover what your heat pump entity name is by creating a global MQTT listener: Create an MQTT in node, set the topic to +/+/+ and link it to a debug node. This is also useful for debugging.
Then, to regularly update the temperature, you can create an inject node, set it to repeat as often as you like, link it to a current state node that queries any entity you like, and then link the result to your MQTT out node.
I also added a 2nd inject node to manually override the temp to 88 deg just to test if everything was working. If you set this 2nd inject node to send a value of 0, it disables the remote_temp, and the heat pump goes back to using its own temp sensor.
Here’s an example: