Thanks Saq, Tones and Jeremy, it was hidden in plain sight.
The reason I need this is a design decision of some zettlekasten-like features I'm implementing in my wiki. For example, tiddlers tagged with Source are the books, articles, or other sources of concepts I want to track and I've modified the view template to show some fields and references to related things in a footer:
Now, I'm introducing buttons to create related tiddlers that have the kind of relationship of the corresponding tab. Sometimes that means copying current title in the author field. But in some case I need to set current title in title list format because of the meaning of the field. For example, a concept might have two authors.
BTW, this is pretty much inspired by the amazing Soren's zettlekasten. Thanks Soren!