The field is used in the mixer to name the track. My library is the same size as yours and it took me weeks to organize everything. (track name, position, color, transpose) Not to mention I set up all the regions and song info too. Glad that's done!
I know there's a couple current threads discussing the process of importing songs and getting your database up to speed with all of the new features of ST4. And there's been a few threads from the beta too, to which I shared the same concerns about what can be done to speed up the monotony/repetitiveness of it. Hopefully, one day a reasonable solution will be found.
One feature that was added that may help some is the "Apply to similiar tracks." https://stagetraxx.com/docs/v4/song-details/audio/track-details/#apply-to-similar-tracks
This, however, doesn't work for me because my songs aren't consistant past track 3. I do Click, Cue, Drums, Percussion (maybe), Bass, etc. Some songs have more than one guitar track, or more than one keys track, some horns, or a SoundFX track. So I'd hate to overwrite songs that I've already organized by using Apply to Similar Tracks.