You can export the quantities with the custom fields export selector. You can edit and upload the fields back into the StoreAutomator.
Here are the steps:
1- Select the products and go to Export>Custom…
2- Select the fields from the Quantity section.
3- Download the file from the “Notifications” from the top right.
These are the fields in the file.
IMPORTANT NOTE: “all_fulfillable_qty and default_fulfillable_qty” are the read only fields.
IMPORTANT NOTE: If you want to delete a specific field data, you must leave the cells as empty. This action will delete the data which you have already in SA, when you upload the file back into SA.
4- After the changes, upload the file back into SA.