is even possible to add new song, but with that i mean the music, moves and gold moves? because this method seems that only add music but everything else is from the original song D:
It would be really hard to add your own moves.
/cache/itf_cooked/nx/world/maps/[tracktitle]/timeline/pictos contains move icons that are ckd formatted (I think it's just a matter of trimming the file header to depackage it).
/cache/itf_cooked/nx/world/maps/[tracktitle]/timeline/[tracktitle]_tml_dance.dtape.ckd contains some parameters in plain text, like when a move happens and is it a golden one, but it only defines sensor parameters for Xbox One and PS4.
/world/[tracktitle]/timeline/moves/wiiu actually contains sensor parameters for Switch but they are all written in binary so not sure how to edit it.
P.S. If you managed to get Just Dance China ver. for Switch which contains 4 exclusive offline tracks, you can see they aren't charted for Xbox and PS4 at all. Their sensor values are all the same dummy ones.