Let customers reduce or remove itemsOn by default. Turns off just this mode and leaves the rest on.
Let customers increase quantityOff by default. Also needs "Allow charging for added items", because raising a quantity can raise what is owed. You also set the most a customer can add in one go.
Let customers swap size or colorOff by default. A customer swaps an item for a different size or colour of the same product, never a different product.
Let customers swap to an option that costs a different amountWhen on, a customer can swap to an option with a different price. If it costs more they pay the difference through Shopify's own payment page. If it costs less the difference comes back.
Allow charging for added itemsOff by default. No money is collected without this turned on.
Keep at least this many itemsCustomers cannot empty the order. Set the smallest number of items an order may be left with; the lowest value is 1. To cancel, a customer uses Cancel order.
When a shopper removes an itemRemove it right away, or Ask me first. In Ask me first, nothing is removed or refunded until you approve it in Tacey or in Shopify.
Where the refund goes, restock, and shippingWhere money goes back, whether the removed item returns to your stock, and whether shipping is refunded on a partial reduction (off by default).
Approve or decline requests automaticallyBoth are off by default. Tacey can approve a request that passes every rule a customer's own removal passes, or decline one that can no longer be cancelled, with a note in your words.
Only if it is in stockApplies your own Shopify inventory settings, so a product you allow to oversell is always offered and a tracked one you do not is refused past its available quantity.