Designating a task as a Template should remove it from your normal lists with no further action on your part. However, you should still be able to assign contexts to templates if you want. Templates should appear in their own list, as a group.
In Astrid, flag your task templates by using the Templates list:
- Click to open the task.
- Click the Add another list… field, then type Templates.
- Press Enter.
- Click Templates (under Lists at the lower left panel).
- Create the new template as a task.