mapping AD CUSTOMIZER - MULTIPLE_MAPPINGS_FOR_PLACEHOLDER_TYPE

Hi, I'm trying to create a mapping for an AD CUSTOMIZER feed. I need to map 2 different attributes to the same field. In the doc it's written "This placeholder type permits the FeedMapping to map

FeedMapping - Map multiple FeedAttributes to the same placeholder fields

Hi, In this documentation (https://developers.google.com/adwords/api/docs/appendix/placeholders) it's written that I can "map multiple FeedAttributes to the same placeholder field.", but when I am tryi