The Edit command opens a block occurrence for you to edit its graphical elements in the context of the surrounding objects on the sheet. This is helpful when you are drawing blocks to mimic assemblies, and you want to position a block relative to another block using dimensions.

While editing in context, you can select surrounding 2D elements and add them to the block using the Add to Block command. You can use the Remove from Block command to remove geometry from the block.

All occurrences in the document are updated to display the modified graphics when you choose Home tab→Close Block→Close and Save on the ribbon.

You cannot edit a nested block in context.