Never used it yet for publishing (only reglar exports), but one thing to note: it must be called before rendition task is started (whether implicitly or explicitly).
When you say "doesn’t work" - what do you mean?
Thanks for your reply. When you say rendition task, if you mean the processing of each photo, then yes, I did place it before that. By doesn't work, I mean: when I publish photos to flckr and watch the progress bars in Lightroom, the title defined in the code doesn't appear. the only thing I can think of, is that it will only show if used through the Export process. If that's the case, why put it?
By rendition task, I mean the background one that is started implicitly by calling export-context:renditions() or explicitly via export-context:start-rendering().
So, is there a title up but its not what you expected, or is it just blank?