Completed tasks do not go away
I am primarily using the web platform with Chrome - although the behavior is the same in Chrome, Firefox and IOS.
Most of my completed tasks always seem to stay - greyed out with a line through them. I understand that subtasks should have this behavior, but I was under the impression that complete tasks within a project / subproject should be "hidden" when complete.
There are additional completed tasks that show when I click the show completed tasks button.
This was becoming cumbersome - as new tasks added to a project tend to be sorted toward the bottom.
Where this was most cumbersome was in a particular sub-project. With 20-30 completed tasks that take up the primary view. I moved this sub-project out to the project level - and the behavior cleared up in all of the other projects.
The completed tasks are still showing in this project though.