I unified all metals to use Thermal Foundation's, including Lead. That means I can't get Eidolon's Lead, and I can't change the Mind-Shielding Plate's recipe to use TF's Lead.

This is a known issue since at least 6 months.
Would suggest using Eidolon Recipes if you want to have JSON support of Eidolon.

it can't edit the existing ones. D: thats what I need/want. so, looks like I gotta wait and hope they get to it. :V

Will be supported officially in 1.18.

I don't really have the time to support both versions; as you can tell from the hiatus I barely have the time to work on Eidolon at all...so unfortunately a backport is unlikely. :/

yeah, you work on mystical world among other things with a bunch of other modders like noobanidus etc don't you? Well... on the bright side the cauldron isn't exactly automatable with ease, atleast not obviously. so if people want to make high yield gunpowder or low cost gilded fruits to cheese out some EMC by hand, I guess they can. cause it takes a while to do, and you can stuff it up... so it's not hyper important, unless people are really intent on breaking my video game the long way around...

............................................ sigh well that does me no good with balancing my 1.16.5 pack which likely has to wait for all existing mods to be updated first, with a high potential of some not actually being so... but ok... :V

I don't really have the time to support both versions; as you can tell from the hiatus I barely have the time to work on Eidolon at all...so unfortunately a backport is unlikely. :/

For people needing JSON Support in 1.16, there a unofficial mod that provides that:
https://www.curseforge.com/minecraft/mc-mods/eidolon-recipes