You can archive a task or milestone by hovering over and selecting the ‘Archive’ button.

If you would like to see and retrieve anything archived, select the ‘see archived’ box on the top left of your project.

Now you can see all tasks and/or milestone that have been previously archived. To retrieve a task hover over it and click the ‘restore task’ icon.

You’ll be asked if you’d like to restore the task. If so, click ‘Yep’.  It’ll now be back on your live project board.