How to reverse auto-populate record number of auto-created BP on line item of source BP

I have a scenario where a non-workflow BP is auto created from the line item of a workflow BP/

I want to reverse auto-populate the record number of the auto-created BP back into the corresponding line item of the source BP after it’s created. I intend to use this record number later for data picker filtering.

I tried using a Text data element on the source BP line item, but in the Reverse Auto-Population setup, there was no option to select the auto-created BP or its record number field.

Is there a specific data element type required on the source BP line item to make reverse auto-population work?