Hi! Thank you.
The idea is to just use Auto Playlists. The Static playlists, at the moment, are more of a means to an end, because I currently have a big bulk of songs (over 30k) that I need to organize, according to the genres I have defined, and place them into playlists. Speed-wise, it's more productive for me to just drag the songs to the static playlists on the side tab (that have the same name as the auto/smart playlists in iTunes) and, once finished with this large bulk, just append the playlist code to the Grouping field of the songs in each playlist. In this case, I avoid typing which would be more energy and time-consuming for such a large amount of songs.
After all that is finished, for the few new songs that I will occasionally add, I believe it's just better to type the playlist codes on the Grouping field directly as I organize them, which will result in an instant update of the files' metadata (in MusicBee, since for iTunes, these files would still need to be 'refreshed' so that they reflect the updates in the tags which can be done by playing them once or with the help of scripts).
So basically, I was just looking to optimize the workflow here. If could choose, I'd rather always use the dragging method, if I was able by doing that to also have the codes simultaneously written in the Grouping field. In the past, I'd have simply used static playlists in iTunes and dragged the songs into them but these days, I prefer to have those codes embedded within the music files themselves, just in case something bad happens to the library or the playlist files, or if I change directory.