This addon lets you search text inside the default (str) subtitles of the current playing video
and takes you to the moment in which the selected line was spoken (press Goto button).
Copy the file in the VLC subdir /lua/extensions, by default:
* Windows (all users): %ProgramFiles%\VideoLAN\VLC\lua\extensions\
* Windows (current user): %APPDATA%\VLC\lua\extensions\
* Linux (all users): /usr/share/vlc/lua/extensions/
* Linux (current user): ~/.local/share/vlc/lua/extensions/
* Mac OS X (all users): /Applications/VLC.app/Contents/MacOS/share/lua/extensions/
(create directories if they don't exist)
Restart the VLC.
Then use the extension by going to the "View" menu and selecting it.