Common tasks

List the categories and how long their lists are.

foreach (LootCategoryInfo category in LootPools.Categories())
    Log.Info(category.Name + ": " + category.CommonWeight + " common, " + category.RareWeight + " rare");

See what one category contains.

foreach (LootEntryInfo entry in LootPools.PoolFor("Cupboard"))
    Log.Info(entry.Tier + " item " + entry.ItemId + " x" + entry.Weight);

Take your item out of a category again. Remove returns true when your mod had an entry for that item.

bool removed = LootPools.Remove(Mod.Id, "Cupboard", 14780);

Put an item in the rare list. Do this only for a category that already has rare items (see the rules below).

LootPools.Add(Mod.Id, "Toolbox", 14780, 1, LootTier.Rare);