Chad Weidert

It is a Zendesk item, and it's covered here under custom field filters. https://developer.zendesk.com/documentation/custom-data/v2/searching-custom-object-records/

You must use the advanced parameters in ‘Get items’ and enter the ODATA filter. The column name will be equal to the Field ID of your customer field as it is shown in Admin. e.g. 21551888334743.