LootTweaks uses the LuaBlock system I developed for CondensedOres - and which now is used for custom CC and RC recipes, among other things - to specify changes to the loot tables present in the game.
These files go in /config/LootTweaksChanges.
It supports the following operations:
- Clear Loot Table
- Remove Item
- Add Item
- Change Item Weight
- Change Item Chance Bounds (ie min and max chance per slot)
- Change Item Count Bounds (ie min and max count per slot)
- Change Item NBT
- Add "Tier" (see below)
- Batch operations (see below)
To simplify large-scale changes, it allows for the definition of "change batches" which can be applied as a unit, so that if you have the same, say, 48 changes you wish to make to 7 tables, you only need to define those 48 changes in a batch, and then apply that batch to the 7 tables.
It also allows defining groups of items as a "tier", so you can set groups of items by rarity for spawning, rather than defining a bunch of item types as functionally equivalent.
It also supports dynamic configuration reloading with the command.
The mod's GitHub repository contains some sample files:
https://github.com/ReikaKalseki/LootTweaks/tree/master/Example Scripts