Since GeeXLab version 0.9+, a Direct3D 12 renderer plugin is available in the Windows versions (32 and 64-bit).
Introduction to Direct3D 12 Programming with GeeXLab

3D Programming, Prototyping and Gamedev with GeeXLab
Since GeeXLab version 0.9+, a Direct3D 12 renderer plugin is available in the Windows versions (32 and 64-bit).