When a 3dm model is opened and Rhino detected the external files of embedded and linked blocks are modified, the Block Definitions to update dialog appears for actions.
Block Definitions to Update
Name
Displays a list of block definitions in the model.
Link Status
Displays the status of block instances linked to external files.
Link File Name
The name of the file that was imported to create the block definition.
Selects all block definition names in the list.
Clears all block definition names in the list from the selection.
Updating the block definitions is postponed until you update manually or reopen the file.
Updates all of the selected block definitions.