When you “Mark Complete” a task it usually signifies that you carried it out. What if you didn’t actually carry it out, but you still want to get it out of your hair–no longer have it appear as Incomplete (active)?
A simple approach that works even with Asana’s free version is to go ahead and mark it complete but also add a tag, perhaps one of #NotDone, #NotNeeded, #Canceled. Since you might want to later locate these, Tag View (click the tag) would allow you to see a list of all tasks with one of those values.
Another approach, if you’re on Business or Enterprise, is to Mark as Approval then set the task to Reject. That’s more elegant, but there’s a drawback if you’re hoping to be able to find all of those “rejects” down the road: You can’t search for Reject. (Oddly, you can search for tasks that are of the Approval type, but not specifically “Approved” ones or “Rejected” ones. To vote for that feature, go to
How to search "approved" tasks?).
Other methods exist too; multi-homing to a project like “Not Done,” “Not Needed”, “Canceled” is another way. Do you have another favored approach? Do you like one of the ones mentioned here?
Thanks,
Larry