Multi-site MQTT Topic

I plan to deploy several raspberries with node red and an MQTT broker to monitor in a "PCVUE" hypervisor.
Each site has a 4-digit number in a text file in /home/pi/Documents/sitenumber.txt .

My node-red has a lot of in or out topics, I would like to be able to modify all the topics by modifying the text file.

example topic: /site n°/bedroom/temp

Thank you for your help

In Node-RED version 2.1.1, the mqtt node allows dynamic subscriptions. Take a look on the 'Help' tab when hi-liting the mqtt node.