When you buy the same item from more than one supplier, Reorder can group its suggestions by whoever last charged the least, so the draft purchase orders it creates go to the cheapest source. Recording those suppliers on each item is covered in Buy the same item from more than one supplier.
Group by lowest cost
The note on a purchase order line leaves the choice to you. When you would rather have Stockroom make it, Reorder can group your suggestions by cost instead of by supplier.
Above the suggestions, switch the grouping from By supplier to Lowest cost. Every line that had a cheaper price on record moves under the supplier that charged it, and a strip at the top totals what the regrouping saves - Saving about $66.64 across 7 lines. If nothing can be improved it says so: Every line is already at its lowest known cost.
Moved lines carry a was Distributor A hint with an Undo beside it, so you can send any single line back to its original supplier without leaving the grouping. A moved line also re-rounds to its new supplier's minimum and pack size, because the case you have to buy from one distributor is rarely the case you buy from another.
From there, create the purchase orders exactly as you would from any other grouping.
It follows the same rules as the notes on a purchase order, so the two can never disagree: same currency only, and never a supplier you have archived or told Reorder to ignore. Savings are measured against what you actually need, so padding a line up to a case size is never counted as a saving. Where currencies are mixed, the strip reports how many lines moved rather than a blended total - Stockroom never adds two currencies together.
The toggle is a view, not a setting. It changes nothing durable, and tomorrow's suggestions are grouped by supplier again. When one distributor really is the right default for an item, pin it instead: Make primary in the compare dialog, or the Primary checkbox on the item's supplier row. A pinned supplier is the one Stockroom uses everywhere it has to choose.
Stockroom can also set the primary supplier for you, from your own order history: when a Stocky import finishes - and once, automatically, for existing stores - each item with no useful supplier assignment is pinned to the supplier you last ordered it from - and from then on, marking a purchase order as ordered does the same for any of its items that still have no primary supplier, so the first real order names the supplier. Your own choices always win: a supplier you pinned yourself, or a vendor or tag rule you set up, is never changed. The product page leads each item's supplier section with a Current supplier line naming who Stockroom will use and why - From your order history, Set as primary, a vendor or tag rule, or Matched by vendor name - so you can see where an assignment came from, and re-pin or remove it if it is wrong.
To review assignments at scale, open a supplier: their page shows an Items supplied count, and the Price list view marks each item where they are the primary with a Primary badge - tick Primary items only to see exactly what will group under them on Reorder and on purchase order suggestions. On the Inventory page, pick a supplier in the filter row to see everything you order from one company, and turn on the optional Supplier column to see each product's current supplier while you scan.