32 Bit Depth Buffer Switch in 4.22

In the 4.22 change log, it says:
New: Depth buffers can now be switched to 32 bit on D3D11 and D3D12 using r.d3d11.Depth24Bit=0 and r.d3d12.Depth24Bit=0, respectively.

Is this just a console variable, or does that need to be added in VS and compiled? If it needs to be added in VS, which file should we modify to enable it?