Howto: Combine or edit subtitles
Run Subtitle Workshop. Tools > Join Subtitles Check the boxes ‘Load file after join’ and ‘Recalculate time values’. [it will load the new combined file and reset the values on the second part of the subs] ‘Add’ the subtitle files and click ‘Join’. The new combined files will load. Click ‘Movie’ and open the movie file and check the subs sync.