You can update your swatch images by using the vertical image file. After exporting the file, you just need to use valid values if you want to set the related image as a swatch image. The marked image will be sent to the channel as a swatch image.
Here are the steps you need to follow:
1- Select the products, go to “Export>Export Inventory>All Images (Vertical)”. If you are in inventory level go to “Export>All Images (Vertical)”
2- Download the file from the “Notifications”.
3- Open the exported file, and use the valid values to select the related image as a swatch image on the column “is_swatch” column.
Valid values for “is_swatch” column: “yes”, “no”
IMPORTANT NOTE: If you’ve already selected an image as a swatch image and want to unmark it, you can use “no” instead of “yes”.
4- Upload the file back into StoreAutomator.
You can also check the below article about the vertical image file.