Wow! That is fantastic! Well done mate!
I do have a few comments however. First of all, the information screen when you load the editor shows for about a second, so I can never see what it says. Guess that isn't such a big deal, but I thought I'd mention it. No use in having it if I can't read it.
Second, when you load, you should be given a "Choose file" dialogue if it can't find ufo.exe (either way in fact). What happened to me (my .exe is called UFO Defense.exe) is that it couldn't find the .exe, and gave an error message on that. In addition, it created a ufo.exe by itself, that I couldn't delete even if I closed the program. Slightly annoying
Third, you should refine the GUI a little. I would suggest a tab at the top for each ability of the editor. Soldier names, Base editor and so on that can easily be switched between, and that all have the same sized windows.
Fourth, some more documentation coming with the editor, and help inside the editor would be good. Now it didn't take me long to find out that if I clicked the storage items in the right hand window, I could edit the numbers I'd have in storage, but it would still be nice with a little text or something explaining this.
Well, that's a few things from my first impression. If I find more time, I'll test it a little closer. I'll also put up a news post on this.