Most of the movie is in the center, so that’s the large, dense dialog track 3. LFE is frequently processed low and doesn’t have much to do. Four is the smallest track.
There are standard channel allocations for different formats, but they are different for different formats and there is no guarantee that a recording actually uses the standard channels. Audacity just sees channels 1, 2, 3,… and could assume that the channels are “standard” for the format of the imported file but if non-standard channel mapping has been used when encoding, then Audacity has no way of knowing.
The tracks in your screenshot look like they are probably L, R, C, LFE, SL, SR