This has been long overdue, but I finally sat down and created a list of all the additional data ModPlug Tracker / OpenMPT can store in IT / XM format. Some parts may be missing or inaccurate. Please feel free to ask if some parts are not clear enough.
http://wiki.openmpt.org/Development:_OpenMPT_Format_Extensions
+0,5. :)
+ because I like the effort.
0,5 because it took so damn long. :nuts: :D