I completely forgot to say that this update also ships an important fix that was released previously but not updated yet.
I (JY) was contacted by several people that told me that sometimes, in the TrackMate XML files, the edges that link one spot to another could have the wrong orientation. Normally, by convention, all links are oriented towards time: The source of a link is the spot early in time, and the target spot is the one late in time (frame of source < frame of target, always).
Apparently some situations violated this convention. So to avoid this, I changed the way the XML is saved to check the link orientation and to correct if so that it is always in the right direction.
This should simplify things for people importing TrackMate XML files into other softwares.