You can update a Revit project with changes that were made to data in an external database, or that were directly edited during import.
The appropriate Revit elements reflect any changes that were made to the database.
The import table view allows changing of data immediately before import if desired.
You can use Ctrl+0 to set a cell value to empty in the table view.
It is not possible to delete, cut or modify an entire record (using copy and paste) if the corresponding element exists in Revit.
Those tables that do allow creation of new types will have a new row record available. When filled out with all the required data, the ID displays a negative value which converts to a valid element ID after the import process.
The Custom Parameters menu allows you to create Shared Parameters for your project. Click Add and specify the Name, Group, and Type, then select the Categories it will belong to. All selected categories that have an associated database table automatically appends the new parameter field to the table. This parameter data may then be edited in the drawing or the database and updated accordingly upon import or export.
DANGER: Only import from the database originally exported to for a given project, or unpredictable results may occur.