I have a mod that sets the hidden flag on some items and sets the hidden bool to true on some fluids. When I go to the FNEI non-localized search window, it hides all the hidden items from the view, but not the hidden fluids. Would it make sense for FNEI to treat fluid.hidden the same as the hidden item flag? If not, is there another way for a mod to hide them from this window?

Came here to report the same thing, I'm coding angels mods at this point, where FNEI is of great help, but it keeps showing the hidden fluids (which is very annoying). The option to show hidden items should also affect fluids, or have a seperate button (also disabled by default) to show/hide fluids.

What I've done as a workaround (hopefully temporary) is to put all the hidden fluids in a separate subgroup with order "z". That way they at least appear after all the other fluids rather than interspersed with them. Still a bit confusing, but less so.