The following fields can be used in the Custom Fields or Calculated Fields of any type of data export. The leading underscore is intentional to avoid potential conflicts with Shopify API fields.

• _row_number - The row number in the CSV export (note that this won't be accurate when using Custom Filters > User-Defined Fields as these filters are applied towards the end of the export, after Custom Fields/Calculated Fields were already evaluated).
• _current_datetime - The current timestamp at the time of export in ISO 8601 format (e.g. 2019-02-20T19:40:34.530706-05:00). Use with the fomat_datetime() function in a Calculated Field to change the format.
• _shop_id - The unique ID of the Shopify store.
• _shop_name - The name of the shop. (e.g. E Corp)
• _shop_domain - The shop's domain. (e.g. ecorp.com)
• _shop_myshopify_domain - The shop's myshopify.com domain. (e.g. ecorp.myshopify.com)
• _shop_currency_code - The three-letter code for the shop's default currency. (e.g. USD)
• _shop_timezone - The shop's current timezone setting (e.g. America/New_York)

Enclose the fields with double curly braces when referencing them in Custom Fields or Calculated Fields (e.g. {{ _row_number }}).