Configuring the targets for each button with buttons over video is almost exactly the
same as configuring the button targets in menus. You have the option of setting them
in the Connections tab (the buttons appear as marker items), in the Subtitle Inspector,
or by using a shortcut menu in the Subtitle Editor.
The difference is that a button within a track cannot select a specific stream in a different
track. For this reason, the stream settings for buttons in subtitles are inactive if the target
is set to anything other than “not set.”
If you need a button within a track to select a specific stream in another track, you can
set the target to run a script that’s configured to jump to the desired stream.
Setting a Button’s Connection
for details on each method.