Standalone admin program opened from the inventory category menu or direct window links.
Staff select a supplier and manufacturer, view a sortable grid
of products with supplier-specific costs from pd_product_costs, and add, edit, or
delete cost rows. Supplier costs persist in pd_product_costs; manufacturer cost
(custom field slot 3) updates oc_product.custom_field when rows are edited.
Workspace notes
data-parent; changing manufacturer reloads the grid with preserved sort and pagination state.