I first reported this in March 2015 in the GXV3500 Rel 184.108.40.206. The Device Name field is still missing from the Decode Configuration pages. You would think that 5 years later and numerous firmware releases that it would be fixed.
Did you open a help desk ticket on this. If not, that would be the best course of action IMHO.
No I did not open a help desk ticket in 2015. I spoke with a Grandstream Help person I had contacted in 2016 about a firmware update problem. We also discussed the Decode page Device Name. He said that the Device name issue was on a future firmware bug fix list.