In the Project Navigator environment, property data lives in the Constructs. If you set up an Element that has a Door in it, and place it in a Construct, when you tag that Door, a property data override is placed on the externally referenced instance of that Door in the Construct file. That is done so that if you use the Element multiple times, each externally referenced instance of that Door will be seen as a separate Door, with its own property values.
The above holds for properties in object-based Property Sets. If you have a property that should be the same for all instances of a Door of a particular style, put the property in a style-based Property Set. You will then be able to change the value once, on the Style, and it will change for all Doors of that style. Unfortunately, if your goal was to have a property that you could set for a Door in an Element that would apply to all instances of that Door when externally referenced into Construct(s), but that could be different for other Doors of the same style, that is not possible. You would have to decide whether the overhead of creating and maintaining a unique style for that Door would be worth being able to control property values at the style level.
David Koch
AutoCAD Architecture and Revit User
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