With external audio track support planned for version 8.4, hopefully this isn’t far behind.
I’d also suggest, contrary to some other posts in this thread, that when this is implemented, the selection UI shouldn’t be hidden away in an overflow menu, but shown prominently on the pre-playback screen. Otherwise, issues like the incorrect subtitle selection mentioned by @m1et, or cases where playback defaults to a commentary track instead of the main audio (as mentioned here), may only become apparent after playback has already started.