Ok. Yes, that is the latest version. I had thought @Bhaskar added signal strength percentage to the library but it was battery percentage he added.
There are some resources online for converting RSSI to signal strength percentage but honestly signal strength is not really black and white like that. There is no perfect way to convert RSSI to a percentage. This is why cell phones show bars rather than signal strength percentage. I would recommend googling RSSI to learn what it means, then perhaps you could do some conversion of the reading in Node Red as you see fit.
But in the case of the IoT Edge computer, the further the sensor is, the more RSSI it has (80), while if the sensor is next to the IoT Edge computer, the signal is less (40).
In the link you sent it says “0x4 indicates a low signal level”, but on the IoT edge computer the low signal level is 0x50 …