Opens the block definition in the Block Editor.
The Edit Block Definition dialog box is displayed. Select a block definition to edit or enter a name for a new block definition to create, then click OK to open the Block Editor.
If the ribbon is active, the Block Editor ribbon contextual tab is displayed. Otherwise, the Block Editor toolbar is displayed.
When the BLOCKEDITLOCK system variable is set to 1, the Block Editor cannot be opened.
The Block Editor is a separate environment for creating and changing block definitions for the current drawing. You can also use it to add dynamic behavior to blocks.