I've lots of completed tasks in Google Tasks since using it for couple of years. And I wonder how to clear the competed tasks list. Regarding this Google Groups discussion, which is closed due to inactivity, it's not possible.
But I've found one solution: it's marking completed tasks as uncompleted and deleting them from list. It's ok for coupled of tasks, or maybe tens, but not for thousands.
Is there any way to permanently delete them, once and forever (except completely deleting the Google profile)?
PS: I've also fount out that it takes up to 1 month to delete those tasks from Google servers completely, which is quite some time.