You can submit a release split into multiple discs (Disc 1, Disc 2, Disc 3, etc) if it meets these 3 requirements:
It's an Album-type release (does not apply to Single or EP).
It must not be distributed yet.
It must have 7 tracks or more, or a total duration of over 30 minutes.
How to create a Multi-Disc release
Click New Release.
Fill in all the album-level fields.
Upload the tracks. If the album has more than one track and meets the requirements above, the "Split into discs" button will appear at the bottom.
Click it and assign each track to the corresponding disc. At first you'll only be able to choose Disc 1 or Disc 2; once you create the second one, Disc 3 becomes available, and so on.
Move to the next step, add DSPs and territories.
Submit the release so it reaches our quality control team.
Things to keep in mind
Changes are saved automatically, there's no need to save manually.
To move a track to another disc, use the disc selector, don't drag it: dragging only works to reorder within the same disc.
Discs are always numbered consecutively starting from 1; if a gap is left (for example, Disc 1 and Disc 3 with no Disc 2), the system renames them automatically.
Once the album has been distributed, the disc organization is locked: you can't reassign a track's disc or revert to a single disc. You can still reorder tracks within each disc.