An addFluid method for adding hidden fluids
Ex:
mods.jei.JEI(fluid:tconstruct:molten_silver);
(Molten Silver is hidden for some odd reason so it'd be nice to add it back)
Also, possibly a /ct dumpHidden command to see every item that's hidden whether through scripts or by the mod maker's design, useful for finding stuff like this.

(Did you know, Thermal Series has a hidden Nuke item?!?!)

Fluid addition is now supported in CraftTweaker