i don't believe you can. i think it's hardcoded, as is much of the GUI. substantial changes to GUI have been done through bypassing it through making another feature (e.g. filters for buildbar). however, i don't see how this could be done, here. i believe the history tab to be hardcoded. however, don't take my word for it. i don't know a great deal about this sort of thing.
what about creating a techtree for the black sun
as I know creating a new tech tree could be done in Microsoft Visual Studio by editing guidialogs.rc It can be also done in other programs but VS has graphical "overview" so you will see how it will be. Maybe it can be used to create that faction history but I haven't looked for this yet.
Yeah, I'd also check GUIDialogs.rc concerning your original question about the history graph. I wouldn't necessarily be optimistic about finding anything, but just for certainty...
http://www.everythingeaw.com/showthread.php?t=2928 that's how to add units to a tech tree. however, i don't know about making a tech tree for a faction...
seen it, doesn't help alot, but thanks guys.