I wouldn't bother trying. Dialogue text I would do in the txt notepads, though.
I used the unofficial editor a couple of times on .90x mods, because it has such a handy map screen which gives you the co-ordinates to place cities etc...
It threw up hundreds of errors just opening the late-version mods, and native. What I ended up doing was exporting the map back to .750 native, editing it, then using the coordinates and map which it produced. Only to discover that soem of the map textures are not compatible, - this dumped me back in 900 with a useless map, although the co-ord.s were still good.
It would, I think, be less damaging and more likely to produce a good result if you were to use the most recent python system, rather than the UE.