Price and stock per colour/size (variant pricing)

If a product has options (e.g. colour, size), the product editor lets you set a separate price, old price, and stock for each combination (e.g. "Red / L") next to the options block — leaving a combination's field blank means it inherits the product's overall price/stock. Up to 200 combinations are supported. Once any combination gets a stock number, the whole product switches to tracking stock at the combination level. Where to find it: below the Options block there are two checkboxes — "Price differs by variant" and "I track stock separately per variant"; until either is checked, one line tells you every variant sells at one price. Once checked, a table of combinations appears — a blank cell means "same as the product". Unchecking it clears any per-combination prices/stock you already entered and asks you to confirm first.