Sharing in case anyone else needs this information later.
This is the track to language mapping for the 4K/UHD Frozen II disc.
00800 = English
00801 = French
00802 = Spanish
00803 = Japanese
00700 = English (Sing-along)
00701 = French (Sing-along)
00702 = Spanish (Sing-along)
00703 = Japanese (Sing-along)
The only difference between the 008xx and the 007xx series are the subtitle tracks. The 007xx series has subtitle tracks that only contain the song lyrics. The 008xx series has subtitle tracks containing all text, spoken or sung.
If you're like me, it makes for more work than should be required to get a single mkv that supports multiple audio tracks in different languages and that can be used to play sing-along subtitle tracks in those languages as well, so knowing which track is which can save a lot of time when ripping the tracks you need to remux together afterwards.