In the old 2.x interface, if an album had multiple discs, the track listing would include small headers at the start of each disc in the track listing. This has been changed in 3.x:
As you can see in the picture, there is no indication of disc number; the track numbers just roll back to the first track’s track number at the start of each disc. Please bring back the “Disc x” header that used to be at the start of each disc.
