You have to be more specefic, what do you meen by treee of improvents? the tech tree? Each research is a single file in the gameinfo, starting with "researchsubject... .entity". You will need the gameinfo files for your version of sins as text files, you can seach for reference files to get the files for the newest version.
To make the mod, make an folder in the mod folder of the game (go in options in the game and then mods and press show modfolder or something like that) with the name of the mod. Then create a folder named GameInfo in the modfolder. Copy over the files you want to edit from the reference folder to the GameInfo folder and edit them with notepad or another text file editor (note that by text file I don't mean files like word files).
I hope this helped.
