If you looked up the data in the Editor directory, replace Data\Public\<MOD-NAME> with Data\Editor\Templates below. If you unpacked the games Main.pak to look up the data, the <MOD-NAME> below would be either 'Main' or 'Shared'.
The files you need are not actually XML files but simple text files (with some pre-defined syntax).
1. Look in Data\Public\<MOD-NAME>\Stats\Generated\Structure\Modifiers.txt for possible modifiers for different entity types (weapon/armor/object/character/...) and in Data\Public\<MOD-NAME>\Stats\Generated\Structure\Base\ValueLists.txt for the definitions of the data types used in Modifiers.txt.
(Some types are self explaining, you know them if you are a programmer.)
2. Boosts used in crafting link to boost entries in Armor.txt (Weapon.txt/Shield.txt/where-ever-else) via Data\Public\<MOD-NAME>\Stats\Generated\DeltaModifier.txt. In thi file, there are the also the prefixes and suffixes used for certain boosts. (I don't remember out of memory if those prefixes/suffixes are used when boosts are crafted onto items, never created new ones myself.) There must be some further translation of the pre- and suffixes into strings that have a 'handle' that points to the localization file, which is inside Data\Localization\<LANGUAGE>.pak. Since I never created any new prefixes or suffixes but used existing ones, I do not know how you can introduce new ones into the game.
Somebody else might know that.
Example:
The boost entry
new deltamod "Shield_Small_Durability_Mod"
prefixname "Well made"
suffixname "of the Smith"
param "ModifierType" "Shield"
param "MinLevel" "1"
param "BoostType" "ItemCombo"
new boost "_Durability_ShieldBoost",1
links (via 'new boost ...') to an entry in Shield.txt
new entry "_Durability_ShieldBoost"
type "Shield"
using "_BOOSTS_Shield"
data "Durability" "2"
data "Value" "3"
The boost entry has the 'prefixname' and the 'suffixname', the 'param "BoostType" "ItemCombo"' makes sure the boost is never chosen for drops, 'ItemCombo' somehow means 'used for Crafting', although Crafting can use any other boost type too.
As said, I do not know whether prefix and suffix come into play in Crafting and I don't know how the actual strings are transformed into the final displayed strings.
