I don’t use a Fibaro Home Center, but the individual valves integrated into HA, so I can’t help you on this.
But, I have some valves without the external sensor and to show the current temperature which would be at 0, I use a python script.
See if it helps you.
otherwise here he explains how to do it, even if it is in Italian.
https://henriksozzi.it/2021/04/trattare-lo-stato-di-unentita-in-home-assistant/