hello @Lance, welcome to the Tulip Community!! it would be great if you can introduce yourself here: Welcome to the Community, let's meet!.
the only thing you need to add to the request are square brackets around the ID of the linked field. even if it’s a 1:1 relationship in the linked field, the API endpoint is expecting an array. something like this should work:
{
"ID": {{Record ID}},
"EfuYKrneFcwKzcuqG_link_left_column": ["001"]
}
here’s an example:
let me know if this helps and if you have further questions!! thanks for posting.