Use os métodos RAMCategory.getSubCategories() e RAMCategory.getSubCategory(String subCategoryName) para buscar todas as subcategorias de dentro de uma categoria. Se esse esquema foi buscado por meio de RAMAsset.getCategorySchemas() ou RAMAsset.getCategorySchema(String schemaName) ele conterá apenas as subcategorias que estão configuradas ou contêm subcategorias configuradas no recurso.
//Get all sub categories for a category
RAMSubCategory[] subCategories = (RAMSubCategory[])modelCategory.getSubCategories();
//Get a sub category by name
RAMSubCategory foreignSubCategory = (RAMSubCategory)modelCategory.getSubCategory("Foreign");
//Get a sub category given a path to from the category
RAMSubCategory camrySubCategory = (RAMSubCategory)modelCategory.getSubCategory("Foreign/Toyota/Camry");
//Get a sub category given a path from a sub category
RAMSubCategory accordSubCategory = (RAMSubCategory)foreignSubCategory.getSubCategory("Honda/Accord");