The custom music discs created using the Etched mod on 1.18.2 cannot be placed in the jukebox upgrade slot in the backpack. If this would be a possible thing to implement I would be eternally grateful!

This is still an issue on 1.19.2

Hopefully support is added in the future :)

Given that we now have sounds stored in components in 1.21 if Etched ports it should use those and custom disks should just work in jukebox upgrade so I am closing this.