I promised @alexcjohnson that this editor would somehow indicate to the user when the value of an attribute has been explicitly set or is currently just following the underlying default, and that there would be a way to 'clear' the current setting. For example, if the color of a marker is blue, is it blue because the user set it to blue, or is blue the default? If it's the former, then we should be able to reset it to the default, even if the default is the same blue.

My current best-guess around what this could look like is this, with some more careful thought paid to the colours:

The dynamic UX would involve a tooltip on hover with a bit of explanatory text and the option to double-click to reset to defaults.

Thoughts @VeraZab ?