If you want to get rid of lists you no longer want, you can either archive them or delete them. Archived lists are hidden from the workspace yet still accessible, but deleted lists are permanently removed.
To delete a list, click the
... menu in the top right corner of the list and select, "Edit." After clicking "Delete" and confirming the deletion, the list will be completely removed from the workspace but its tasks will be placed in Trash.
Tasks from the deleted list will remain in Trash for 30 days before being automatically deleted. However, if any tasks from the deleted list exist on any active lists, they will not be affected.
Remember, deleting a list is not reversible, but archiving a list is!