Tasks with the status of “Complete” don’t show in the main tasks kanban view.
The “Complete” kanban column is there so you can drag and drop tasks to mark them as Complete but you can’t see all tasks that have previously been given this status in this column.
The reason for this is because once you have many tasks with the “Complete” status this would result in the “Complete” column becoming very long and hard to use.
Tasks with the “Complete” status can be seen on a project by project basis.
To see tasks with this status on a specific project go to the Tasks List or Tasks Kanban page when you’re in a project and then click on “View Completed Tasks”. This will then show tasks with the “Complete” status on that project alone.
As you are viewing tasks with this status on a single project only it limits the number of potential tasks that will show to just tasks for that project.