So, how do I make it so a reaction uses, say, 10 bars of one metal and gives 1 bar of another metal?
Reaction products and reagents work as follows:
[REAGENT:INTERNALNAME:QUANTITY:ITEMTOKEN:MATERIALTOKEN]
[PRODUCT:PROBABILITY:QUANTITY:ITEMTOKEN:MATERIALTOKEN][PRODUCT_DIMENSION:NUMBER]
This example has no modifiers on the reagent, and one on the product.
Internal name is simply so you can reference the material. For instance, if you want the product to be made of the same material as that specific reagent, like with a lot of reactions that produce furniture in the base game.
Quantity seems straightforward at first, but you need to keep in mind that for things like bars and thread, quantities are different. A single bar is 150 units of that metal. So multiply 150 by the number you want to request.
Then comes the item token. In the case of bars, you'll want to type in BAR:NONE. By doing this you are saying you want to make a BAR item, which has no subtype. If it was, say, a weapon, you'd go for something like WEAPON:SWORD_SHORT.
Material is much like that. Metals are generally defined as inorganics, so you go INORGANIC:<name of your metal>. If you wanted a creature material, you go with CREATURE_MAT:<creature name>:<material name>. There are some hardcoded materials like amber that take no subtype (so :NONE). INORGANIC:NONE creates magma.
The product follows much the same formula, with some exceptions:
First and foremost is probability. It goes from 0 to 100, though there's no reason to use 0. Probabilities are independent, so if one product has 100 probability and another 50, it means that the first will always be produced, while the second will only appear half the time
in addition to the first.
Quantity works differently as well for thread and bars. Since you want 10 for 1, here you'd only place 1. The modifier at the end, PRODUCT_DIMENSION, is what will tell it that the product has a dimension of 150. If you wanted 2 bars, you'd NOT multiply the dimension. Instead just put 2 in the quantity field.
All reagent modifiers are here, while
product modifiers are further down.