Update: I found a key sequence that works to report the coal and water levels. You’ll get one or the other randomly. Use the key sequence:
AUX1, AUX3, crew talk
Use while moving. You will get the coal or water level and current speed for steam engines. I don’t have any diesels but I imagine you’ll get the fuel level. I also don’t have any electric engines. Who knows what happens for them. Charge level?
2/26/25 update: The above procedure worked on my legacy scale Hudson, Shay and K4. However it’s spotty on my L1 Mikado. Sometimes it works and sometimes I get a different announcement. Using the Cab3 app the coal/water level buttons always work. So it appears to be engine specific.