Released two REST API fields for enabling pre-orders and for out of stock product visibility.
Get and Update Store profile: allowPreordersForOutOfStockProducts. Allows you to enable and disable pre-orders feature in a store. Read more.
Get, Add and Update product: outOfStockVisibilityBehaviour. Indicates out of stock product visibility behaviour. Read more.

Released the POST method that allows uploading variation images asynchronously. Read more.

New POST requests to add or remove products to an existing category in an Ecwid store referring to its ID. See more details:
https://api-docs.ecwid.com/reference/assign-products-to-category
https://api-docs.ecwid.com/reference/unassign-products-to-category

Added a new array estimatedShippingTimeAtCheckoutSettings which contains information about the settings of the estimated shipping time shown at checkout.

After receiving order information to the shipping URL, now you can respond with custom delivery rates and pickup info along with shipping rates. See more details in Respond with shipping and delivery rates

Now it is possible to track the source of orders. See more details in Help Center
The info is saved in UTM data array containing 3 new fields: utm_source, utm_medium, utm_cmapaign. The saved data is available via Get order request.

Now it's possible to work with product filters in a store through Update store profile request.

Now it is possible to create, update, get and delete custom checkout fields in a store with API requests. The same feature is coming to the Control Panel soon. Read more: Search extra fields.

Now it is possible to create and update manually calculated shipping rates, self pickup or delivery shipping options via API. Read more: Add shipping option & Update shipping option.

New field - lang is added to custom discount and shipping POST request body. Now you can see customer's storefront language in these requests: