Thank you Evan,
I finally managed to receive two float data registering their UUID in a single BLE as you pointed out. The problem I had had before was with the selection of the UUID to process the data when a float was received. I usually declare my UUID in caps but appinventor strings for UUID are in small caps so the condition to know what float I was receiving never matched!
Just for the record, these are the blocks:
I also include the piece of debugging code that helped me to find the mismatch between the characteristic UUID (in small caps) and my string (in caps).
Thank you both for your help!
Regards