Here is the builder side:
The merge syntax isn’t IN the ui-only reference field, it refers to the value OF the ui-only reference field. The merge syntax itself is being displayed in the section header of a field editor which just contains only the field in question.
I’m using a ui-only reference field because I wan’t the user to be able to select the right record from a lookup, but I don’t need to store it in salesforce anywhere.
Can we not use row-level merge syntax in field editor section headers? Field editors definitely have a single row in context.