I’ll need to get this confirmed, but I think you’ll find that the VMB8IR responds to the first 8 IR commands of the 36 commands that the VMBGPOD recognises.
Basically, the Velbus IR commands simulate button presses.
1 to 8 for the VMB8IR
1 to 32 for the VMBGPOD, with 33 to 36 being thermostat mode selection.
This Android app is a good example.
It’s basically similar to what your Harmony remote can do, but on your (IR blasting) smartphone