Hi,
Commit 0fb11bd adds support for reading the disc number and disc count fields from mp3 files. These fields are added to the metadata map, so pretty much any screen that shows the track number can now also the disc number and disc count as required with the 'discnum' and 'disccount' fields respectively.
Commit a9e8f44 adds 'discnumspin' to the editmetadata window.
You may wish to update your themes accordingly.
Richard.