This function will use the default "jet_rel_default" table in JetEngine to look for the post_id of the parent and return its relations from the "child_object_id" column. If you're using a separate table for your relations, you can change the $table_name value.
- Add a New Field in WP All Export (see https://d.pr/i/OW9dze).
- Set a name for the column and use "ID" for the field to export (see https://d.pr/i/v5Mq98).
- Modify the function as needed, paste it in the Function Editor and paste the name of the function in the "Export the value returned by a PHP function" field (see https://d.pr/i/2c6c07).
- The function will return a list of IDs separated with pipes by default, but if you want to export the titles instead, you need to change the $mode in "function my_export_je_relation ($post_id, $mode = 'id')" to "title".