Once a shopper reaches checkout, the usual way to fix a mistake is to go back to the cart. Most people do not. They abandon instead. The checkout cart editor puts a small set of controls under each line in the checkout order summary, so the wrong size or the wrong purchase option can be fixed on the spot. Find it under Grow order value → Checkout cart editor.
Shopper changing a variant inside Shopify checkout

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What the shopper can do

Change the variant

A dropdown under the line lists the product’s other variants. Picking one swaps the line in place.

Switch purchase option

A second dropdown offers Buy once or any subscription plan the product sells, each showing its frequency and its savings.

Remove the item

An optional, discreet Remove link. Off unless you turn it on.
Quantity is not part of the editor. Shopify’s checkout does not expose a quantity control on a line, so a shopper who wants two of something still goes back to the cart.
A few behaviours worth knowing, because they are deliberate:
  • Only variants that are in stock are offered. The one already in the cart is always listed, even if it sold out after being added, so the dropdown never misrepresents what the shopper is buying.
  • The dropdowns only appear when they have something to say. A single-variant product gets no variant dropdown. A product with no subscription plans gets no purchase-option dropdown. A line with nothing to change renders nothing at all.
  • A subscription follows the shopper across a variant swap when the new variant sells the same plan. When it does not, the line falls back to a one-time purchase.
  • The savings badge is calculated, not typed. A plan that takes 20% off shows “Save 20%” on its own.

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Settings

Every toggle on this page applies to the whole store. There is nothing to configure per product. The three sub-toggles grey out while the master switch is off.
Checkout cart editor settings page in the CartSella admin

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Place it in the Shopify checkout editor

This one is not a theme block. It lives in Shopify’s checkout editor, which is a separate editor from the theme editor, and it will not appear on your checkout until you put it there.
1

Save your settings here first

The block reads this page every time it renders. Saving afterwards means opening the checkout editor to look at settings that have not been written yet.
2

Open the checkout editor

Click Open checkout editor in the sidebar of this page. It opens Shopify Settings → Checkout in a new tab. From there, click Customize on your live checkout profile.
3

Add the app block to the order summary

In the checkout editor, select the Order summary section, click Add app block, and pick CartSella — Cart Editor.
4

Save the checkout

Click Save in the checkout editor. The controls now appear under every eligible line.
Adding the CartSella cart editor app block in the Shopify checkout editor
Checkout app blocks require a Shopify plan that allows checkout customization. If Add app block is missing from your checkout editor, that is a Shopify plan limit, not a CartSella setting.

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What is never editable

A gift belongs to the offer that granted it, so its variant, its plan and its removal are all locked. Removing the item that triggered the gift is what drops the gift, and that happens on its own.
Standard bundles, build-your-bundle and build-a-box lines are priced as a set. Editing one line of a set inside checkout would break the set, so those lines show no controls.
Everything else, meaning ordinary items the shopper added themselves, is fair game.

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When a shopper edits, discounts follow

Changing a line in checkout re-runs your offers against the new cart. A shopper who removes the trigger of a gift with purchase loses the gift. A shopper who switches to a subscription can pick up a gift that only subscriptions unlock. None of this needs a page reload, and none of it needs a setting.
Turn Allow removing items on if your support inbox is full of “I ordered the wrong one” messages, and leave it off if your worry is average order value. It is the one toggle here with a real trade-off.

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Troubleshooting

The block has almost certainly not been added in the checkout editor. It is a separate step from the theme editor and from the app embed. Follow the placement steps above.
Expected on a single-variant product with no subscription plans, and on gift or bundle lines. Check a line you know has several variants.
Sold-out variants are hidden on purpose. Only variants available for purchase are offered.
Save this page, then reload the checkout. The block reads the saved settings, not the ones still open in your browser.

Cart settings

Every tool in the Grow order value hub.

Delivery rules

Hide, rename or reorder shipping methods at checkout.