Each postfx_param contains the following fields:
1) id (string).
2) flags (int).
3) tonemap operator type (0,1,2,3).
4) shader parameters1 [ HDRRange, HDRExposureScaler, LuminanceAverageScaler, LuminanceMaxScaler ]
5) shader parameters2 [ BrightpassTreshold, BrightpassPostPower, BlurStrenght, BlurAmount ]
6) shader parameters3 [ AmbientColorCoef, SunColorCoef, SpecularCoef, -reserved ]

define postfxParams1 (PFX1) float4(postfx_editor_vector[1].x, postfx_editor_vector[1].y, postfx_editor_vector[1].z, postfx_editor_vector[1].w)
define postfxParams2 (PFX2) float4(postfx_editor_vector[2].x, postfx_editor_vector[2].y, postfx_editor_vector[2].z, postfx_editor_vector[2].w)
define postfxParams3 (PFX3) float4(postfx_editor_vector[3].x, postfx_editor_vector[3].y, postfx_editor_vector[3].z, postfx_editor_vector[3].w)

module_postfx.py, some intro text here

Postfx Flags

Tthe following postfx flag is available for usage:

fxf_highhdr

Missing description

Other notes

skybox postfx stuff, Vornne, Modding Q&A and Modding Q&A

postfx stuff, dstn, Mount & Blade Modding Discord.