Earlier, two ideas for which custom blending tables can be used were posted: more levels of "usual" alpha transparency, and additive blending. Both are implemented in test/shadexfog.lua. From a Lunatic Mapster32 build, enter the following lines in the OSD (quotes matter):
lua "shadexfog = reload'shadexfog'"
lua "shadexfog.create_128_trans(1)"
lua "shadexfog.create_additive_trans(255)"
This will create blending tables indexed [1 .. 128] for 255 alpha levels and .blend 255 for the additive transparency. Next,
lua "shadexfog.save('SOME_PALETTE_DAT_FILENAME', 0, 0, {{1,128}, 255})"
will save a file with the just created additional blending tables, that can be renamed to PALETTE.DAT and placed somewhere EDuke32 finds it.
To actually use the smooth alpha, you have to add in some scripting code. My
test/sprite_access.con shows how to do this. You'd probably want to control spriteext[].alpha (called *actor[].alpha / sprite[].alpha in CON) and have that translated to .blend + relevant .cstat bits.