Hi Reinhard,
I have no idea why it was not implemented, I checked the code and the library is using the vario IDs to only send altitude, you might raise an issue and ask to add it?
I did a simulation to check vspd latency, SITL is running my patched scheduler and I did not notice any “big” pauses in vspeed reporting.
I realized I told you to use “alt” (altitude) as vario source but I was terribly wrong, please excuse me, the correct sensor is vspd indeed!