The "Product Details" meta box on the right sidebar contains all product-specific configuration. This is where pricing, type, taxes, and company assignment are managed. Purpose: Associate the product with a specific merchant company Dropdown populated from Invoice Plugin company settings Defaults to index 0 (first company or "Default Company") All invoices created with this product will reference this company When empty, uses first company in system If no companies configured, shows "Default Company" Data Source: _product_company_index post meta (integer index) Purpose: Define whether product is Traditional (physical/service) or Digital (downloadable) Traditional - Standard product/service. Normal invoice line item. Always available. Digital - Downloadable digital product with external