How to update one single item within a large package exported with Datasmith

Lets say I got a scene of 100 objects. I export using Datasmith (either 3dsMax or Revit)
I need to fix one object.

How do I update this single object?
Do I still need to re-export the whole scene as a Datasmith file again?

Can I rename objects and re-export to Datasmith and still make Unreal understand what object is what during refresh/re-import?

Lastly, I take the chance to ask what the Datasmith Scene file is, the one that is in the location that you pick when asked asked for importing the datasmith content.
What can I do with it, what can I not do with it?