Thank you for reaching out to the Google Ads Scripts Team.
Please do note that this script has a set function already, and makes use of the field segments.product_custom_attribute4. If you would have any clarifications on how this script should function, I would instead recommend you reach out to the author via the Issues tab of this script's respective GitHub page as they would be better equipped to provide support and insights to a script in which they created. I've included a link below on how you may do so.
|Google Ads Scripts Team|
Glad to help. Don't hesitate to reach out for any Google Ads Scripts concerns.