Under the 'Tracklist' view tab while editing a release in 'Advanced' editor mode if you tick the ⇓ (Collapse Disc), then tick ⇒ (Expand Disc), the tracklist does not reappear.

You have to either tick another tab such as 'Release Information' and go back or the quickest way is to tick 'Return to basic editor', tick ⇒ (Expand Disc) and return to the 'Advanced' editor if you wish.

This appears to only apply to releases with a disc id.
http://musicbrainz.org/release/f5147094-117e-3692-b873-01fe3dc3d1a5

This release w/o a disc id seems to work fine (regarding this action)
http://musicbrainz.org/release/833ae6e0-f6f4-4b24-b42d-6c85c0426670