One file, every supplier
With several suppliers, one file per supplier quickly becomes impractical. The master list is the Pro solution: a single file for your whole catalogue, where a supplier column decides which supplier each row belongs to. Suppliers that don't exist yet are created during import, and the master list's column mapping is saved separately.
The Pro columns
The master list can also carry is_preferred (yes/no — preferred supplier for the product; also settable with the radio on the product's Cost & Margin tab or in bulk from the product list via Edit → Preferred supplier), on_sale (yes/no — sale flag) and sale_start/sale_end (YYYY-MM-DD). As always: blank = unchanged.
The round trip
1. Export under Import → Export. The file contains all products with suppliers, costs, currencies and flags — product_id in the first column makes re-matching bulletproof. 2. Edit in Excel — adjust costs, switch preferred supplier, flag sales. Only touch the cells you want to change. 3. Import the same file. Only filled-in cells are applied, the review shows every change, and everything is undoable.
Template export
The template mode gives you the column headers without data — handy to send to a supplier who should fill in their price list in your format.