Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GTX 980/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 425.31
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: rB26bd5ebd42e3
Short description of error
The shortcut for the big "New" button in Material Properties does not work for the button, which suggests giving a new material to the active slot. Instead it calls bpy.ops.material.new() and silently creates new materials in the data. This can also be tested with Quick Favorites.
Exact steps for others to reproduce the error