I can not screenshot from the building tree view make the modding sector.
Did you use the Steam hotkey for making screenshots (default to f12)? I just tried this in the various building tree views and could do it without an issue, though I only get part of the tree at a time if it's larger than the screen.
Moreover, if I have had a look at a building tree view and open afterwards another race and which also wants to make, this does not go and the programme hangs itself. Nothing at all more goes!
Thanks for reporting this. We will look into it.
Maybe you could save by pressing a button the entire multipage building tree as an image file?
I'll forward this suggestion.