As of the beta 4.0.0, VLC supports dual/secondary subtitles. Making it work seems to currently be a bit fiddly.
First, you need to turn them on, overall. Go to Tools > Preferences > Subtitles/OSD > Dual Subtitles (at the very bottom) > Align and change it to anything but unset. You may also need to adjust the offset (the adjacent setting).
When playing a video, you need to "Toggle secondary subtitle control" with the default shortcut Ctrl+Shift+V. (This means that the normal subtitle control shortcuts like v or Alt+v, for cycling between subtitles backwards and forwards, will now apply to the secondary subtitles, rather than the main subtitles. Pressing Ctrl+Shift+V again will toggle back to having these apply to the main subtitles.) Then, press v the right number of times to switch to the (secondary) subtitles that you want.
Alternatives — mpv
mpv has (IMO) a more convenient approach to displaying two sets of subtitles.
I'm going to assume that all the subtitles are either embedded (as specified in the question) or in a separate, but suitably named external file (e.g. if your movie is called
file1.mkv your subtitle file should be
file1.srt). If not, you can specify the subtitle files explicitly by adding the options
--sub-file=subtitle_file_lang_yy.src etc. or by playing around with
Irrespective of how they were chosen (built-in or from an external file) each set of subtitles will be in its own "stream" when you play the video file. The streams are assigned consecutive, integer indices (1, 2, 3...). In general, the built-in subtitles will (logically) have the earlier indices. The stream indices, their languages (if the subtitle has a specified language), and whether the subtitle comes from an external file, are displayed in the terminal when you play your file with
mpv. For example, after running
(+) Subs --sid=1 --slang=eng (*) (subrip)
Subs --sid=2 --slang=deu (subrip)
Subs --sid=3 'file1.srt' (subrip) (external)
Here the first two subtitles are built-in, with languages English (
eng) and German (
deu) respectively, while the third one is from an external file. The indices (
sid) are 1, 2, 3. The default subtitle stream is the first one (marked with a
(*)) and it's also the one that's selected (with a
Knowing these indices, you can specify the "main" and secondary subtitles with the options
--secondary-sid. For example, to display the English subtitles, from the previous example, as the main subtitles, and the German ones as the secondary ones, you can run (in a terminal):
mpv --sid=1 --secondary-sid=2 file1.mkv
Cycling secondary subtitles with keyboard shortcuts
By default, there aren't any keyboard shortcuts for cycling the secondary subtitles (in the way that you can cycle the "main" subtitles with
J (Shift+j)). However, you can very easily add some.
For example, if you add the following to your
~/.config/mpv/input.conf (or more generally, your
Ctrl+j cycle secondary-sid
Ctrl+J cycle secondary-sid down
then Ctrl+j will cycle your secondary subtitles in the same direction that
j cycles the main ones (increasing subtitle stream index), and Ctrl+Shift+j will cycle them in the opposite direction
J (decreasing subtitle stream index).
(Based on my own answer on Askubuntu.)