How to move lots of tasks out, without losing their completed/uncompleted status?

[Rong Li]

Instead of the default delete task feature, I more often move tasks to the trash folder (like recycle bin of windows), so even a few days later I have a regret medicine for undo it, or for some other analysis purposes (which cannot be done by automatic backup).

However, as the trash folder gets bigger and bigger, starts to affect the performance, I want to move it to another file. We can't use archive feature, because there are tasks that are not completed in this trash folder. Simply copy and paste to a new file seems also not working, because that will lose the status whether a certain task is completed or not (how can I copy/paste tasks WITH its completed status?).

Any solutions? Thanks.