so I've been able to add in some new vanilla potions and enchants without much issues, the examples worked fine. I need to create custom loot however that would be similar to this

item defined in the chest.cfg"
modularmachinery:itemblueprint

NBT Data I need to specify:
{dynamicmachine: "modularmachinery:mana_concentrator"}

I've tried
BLUEPRINT String dynamicmachine "modularmachinery:mana_concentrator"

but it just spawns the item with no NBT data, any help would be appreciated, pretty sure this is user error but in case its a bug I'd be happy to provide any additional info

There may be a version with an alternate system coming out this even, once I have a chance to clear my head of some personal life, test the new version, compile and upload it. You can thank Hubry for the fix / extension.

Want to be a beta tester? Try out this new system and see if you can make it work this way:
http://www.mediafire.com/file/8vsisfk31u18dns/DoomlikeDungeons-1.12.1-MC1.12.2.jar/file

Info / new example here: http://www.mediafire.com/file/7lbikcnzrz127db/nbt.cfg/file

Or just get it where I just uploaded it.

on it! thanks

it's working great now
https://imgur.com/a/aHOgb6n

modularmachinery:itemblueprint, 1, 1, BLUEPRINT
...would be correct for the item (not couting category and level missing at the beginning).

Now where to put the NBT string for that mod I don't know -- they can be complicated. Take the vanilla example:

EEGG5   String   Name "Fortuna Major"
EEGG6   Compound display EEGG5

...where Name has to be put inside display for it to work. If the tag is attached right at the bottom / root / whatever-its-called of the item's NBT (and is correct) it should work if the mod put it somewhere else (or Forge puts all the tags in some place I don't know of) it might not find it.

This is how minecraft stores the NBT for the item
root
->dynamicmachine => modularmachinery:mana_concentrator

Screenshot of NBT edit with a potion for reference
https://imgur.com/a/JO7cHut

the item spawns, as defined in chests.cfg as defined:
heal, 1 modularmachinery:itemblueprint, 1, 1, CONCENTRATOR

the NBT in nbt.cfg is defined as:
CONCENTRATOR String dynamicmachine modularmachinery:mana_concentrator

which coincides with how the potion nbt data works, unfortunately the item still spawns in with no nbt
data, a blank blueprint instead of the machine specific one. I similarly tried this with a botania flask potion that has the entries

heal, 1, botania:brewvial, 1, 1, BOTANIANIGHTVISION
and nbt.cfg:
BOTANIANIGHTVISION String brewKey nightVision

it also spawns in with no nbt at all

I also tried encapsulating the nbt entries in quotes like
CONCENTRATOR String dynamicmachine "modularmachinery:mana_concentrator"

also tried setting it as a Compound tag instead of a string, same thing

and it made no difference. The log file throws the errror:
[08:34:58] [Server thread/INFO] [STDERR]: [jaredbgreat.dldungeons.nbt.NBTHelper:setNbtTag:44]: ERROR! null tag on item item.modularmachinery.itemblueprint

I'm at a loss at this point one what I need to do differently