To Delete a Task or Workflow

In the Customize dialog ( File > Settings > Configuration > Customize ) on the Tools tab, expand the Tasks tab.
Expand the User Tasks section and expand the open DGN library.
Select the task or workflow that you want to delete.
Do one of the following:

Click the Delete icon.

or
Right-click the task or workflow and select Delete from the pop-up menu.

or
Press the <Delete> key.