Kindly note that there is no way to retrieve the
conversion_custom_variable.id and its conversion value into an
ad resource. You cannot use the query which you have provided because ad resource doesn't contain the
conversion_custom_variable.id and conversion_custom_variable.value. Additionally, you can utilize the
Google Ads Query Builder and
Query Validator to build and validate the queries for retrieving the data from the Google Ads API. The only way to retrieve the custom conversion variables using the Google Ads API is by using the
conversion_custom_variable resource. Can you confirm if you were able to view the custom conversion variables along with the ad related data using the Google Ads UI? If yes, I would request you to share the uncropped UI screenshot of the Google Ads account (with visible customer ID) by highlighting the fields and metrics for which you want to retrieve using the Google Ads API.