For the personal board you can remove a task by:
- Changing the task assignee
- Snoozing the task
- Marking the task as completed
- Marking the task as canceled
For the subject board you can remove a task by:
- Unshare the task on that subject
- Marking the task as completed
- Marking the task as canceled
You can also always delete a task, though we recommend marking it as canceled to keep a record it existed, and was discarded for a reason.