The Block editor 
button [Editor-> Selection-> Block editor] allows editing the existing blocks. In the classical menu the command can be found under Draw -> Block -> Block editor. The command is available from the context menu.
When a block definition is edited block references are edited automatically. In order to call the Block editor mode please
1. Select the necessary block reference the definition of which needs editing on the drawing. If there is not any needed block reference on the drawing add it and select. After that the command Block editor will be active.
2. Switch to the Block editor mode in any way that is described above.
3. You will see the selected block appear on a beige colored background which can be changed with the help of the command Background color and Block editor inscription in the mode section. Please perform the necessary changes
4. In order to close the block editor mode right-click anywhere in the drawing field and select 'Close block editor'. Or select another mode of work.
5. To save changes press OK in the dialog box. If you do not want to save changes press Cancel.
In this mode the commands for viewing and editing other objects are temporarily unavailable. To modify the objects of a block the same instruments as in the Editor mode are used.
You can't create or delete an attribute in the Block editor mode. The work with attributes is performed in the dialog box Edit attribs.
Note: If you wish to undo changes that you performed you can do it using Undo 
Redo
(in the quick access panel Undo/Redo) buttons. Please note that undoing changes one by one is only possible if you are still in the Block editor mode. If you exit the mode and press Undo button, all the changes that you performed in the block editor mode will be undone at once.