bluGill parent
Unlikely - a GUI editor is likely to restructure a file on what looks like a trivial change and thus the result cannot be merged.
Why not a GUI editor which instantiates dimensions/coordinates, allowing the user to name/identify them (and then change their values either by changing the associated value or dragging the associated graphical element)?
Where does it put each dimension/coordinate? So long as there is anything that could go in more than one place the GUI can rearrange a file. If the place is specified exactly then a minor change will change the sorting.
I suggested a list/pane at one corner for the actual list --- agree the UI is difficult and that there needs to be a way to set/adjust the association (see discussion on the PythonSCAD Google Group).