Subtitle capabilities available in 2.10/2.11 are described in the wiki "Subtitles". For info about one new project using these capabilities, see the thread "English Subtitles for AI Barks". That project includes development of a TDM subtitle style guide. The thread here is mainly focused on ideas that would require future engine changes to implement.
A. Automatic Switching Between Subtitle Languages Based on Settings
This is a follow-on of a forum discussion between datiswous and Geep.