How can I find missions that have ended but have not been archived?

Begin by clicking on the mission icon. Once here scroll past the columns titled 'Missions that require action' until you see all of your live missions in tile view. In the right hand corner of this section you will see three buttons, click the funnel icon, or the icon closest to the left hand side. From here you will be in filter view and click the button stating 'Mission Status' and you will see a button called 'choose'. Click this and then click the box saying 'ended'. Click apply and you will be able to see all the ended missions.