Air Lord, Engineering Corps
This is a simple addition that is pretty self explanatory but would make the editor that much better.
It would be nice to be able to shift+scrollwheel up/down on the editor panel (blue) to change the size of selected objects if they have any bigger/smaller counterpart.
This way in the basics panel you can select medium propellers, shift-scroll upwards to get the large one, and then downwards again to go to small without even needing to look away from your construction until you need a different type of object, for example.
In my opinion this would make building much quicker and cleaner!