These are unused but working BlendOp options as found inside the GraphicsEngineDX10.dll:
MODULATE_AND_ADD_SRC
MODULATE_AND_ADD_DST
MODULATE_MUL_2
MODULATE_INV_SRC
MODULATE_INV_DST
My discovery was dictated by my hunger of finding a proper solution to the DTV filter which does not work properly in-game with night environments, especially with the much darker nights of my realSKY mod. Below you'll find a comparison between stock filter material data and the custom one using another BlendOp:
Stock MODULATE, day
Stock MODULATE, night
Unused MODULATE_MUL_2, day
Unused MODULATE_MUL_2, night
The main drawback of MODULATE_MUL_2 is that it doubles the MODULATE option, so at day the image is lightened too much than the stock MODULATE. Mind you, the screenshots were taken with the realSKY mod on Unlimited settings, so the post processing effect adds bloom to already bright areas. However, at night MODULATE_MUL_2 brings a big improvement as you can finally see the ground and its objects more easily.
PS: Please admins, pin this topic. The unused BlendOps I found work just fine, and may be useful to other modders willing to experiment with them.