I think the new GUI is officially (kind of) done!
We encountered some weird errors with the scrollbars which is partly why this thread has laid bare for a while. In the end I decided for the sake of getting the release out soon I should scrap the scrollbars altogether for the moment. I made some small image adjustments to fill dead space and make compound bars more readable, and got rid of the editor info button because it was neither informative nor aesthetically pleasing. Maybe we have something else in future, but it's fine for now.
There are still minor bugs here and there. Loading a game still unpauses it. A worst case scenario to fix it would be hiding the menu after loading a game, which isn't all that bad. I'd like the editor help panel to show when the player enters it following the tutorial but not any other time, though this is a small thing. Other than that, the rest of the errors - CO2 flickering, compound totals balancing - can't be fixed by editing the GUI and will have to wait.