I tried to tinker with something using minetweaker and it doesn't seem like osmium is registered with oredict system. Is this intentional?

It is definitely registered - if a mod interacts with the Ore Dictionary, however, is not always the case.

@aidancbrady the "ore:" part is specifically for minetweaker. when setting up variables or references ore dictionary entries, you'd input a ore:ingotOsmium.

maybe i'm using the wrong name for things. would its name be ore:ingotOsmium for instance?

Just ingotOsmium for an osmium ingot.

just to show what I was trying to do:
val AGR_os_nugget = AgriCraft:nuggetOsmium;
val MEK_os_ingot = Mekanism:Ingot:1;

val os_nugget = ore:nuggetOsmium;
os_nugget.add(AGR_os_nugget);

val os_ingot = ore:ingotOsmium;
os_ingot.add(MEK_os_ingot);

recipes.addShaped(MEK_os_ingot * 1, [[os_nugget, os_nugget, os_nugget], [os_nugget, os_nugget, os_nugget], [os_nugget, os_nugget, os_nugget]]);������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������
its not happy with this. Though it IS happy if I use the explicit non-ore-dict entries to add the same recipe. It says something about a truncated class file XD.

Perhaps I should seek help from the minetweaker devs.

maybe if you added your own nuggets and oredicted those it would solve the issue once agricraft adjusts itself to the new version of mek XD

wait.... i see it.
find/replace error ... derp

must've been doing some seriously stupid spelling errors or capitalization derps. Thanks for the prompt response.

@laz2727 this is relevant to my interests - how would I access this hidden mode?

@unpairedbracket It's not part of NEI itself. It's added by NEI Addons or NEI Integration. Check their configs.