done that thingy you wanted partially, you finish it :)

This file is what matters: https://github.com/gajop/Toolbox/blob/153ac5c7963cc15ec8ae9227b9b351ac75e80c51/scen_edit/command/save_images_command.lua.
It's in scen_edit/command/save_images_command.lua.

Everything that gets saved will be saved in your spring folder atm (on linux this is ~/.spring/).
Heightmap gets exported.. but it's really too crispy to be correct.

You can see the partial exported textures if you uncomment this block:
https://github.com/gajop/Toolbox/blob/153ac5c7963cc15ec8ae9227b9b351ac75e80c51/scen_edit/command/save_images_command.lua#L57.
I can't get the merged textures to get exported.
The blitting part isn't working for me, I don't know what the issue is and I don't want to waste more time now. 

PS: Note that I've removed that BAR setting in modinfo.lua, so it will probably reset your modinfo.lua