Keep deleted items
I like to use my to-do list as a perpetual list, so I can go back and reactivate deleted items over and over again (like a shopping list, for instance). I don't want todoist to get rid of my deleted items ever. And I would like to be able to access deleted items from my Android, but don't seem to be able to.
why do you delete them at all, then? Why not simple check them off as complete?
You have access to your completed items and can re-use them as needed. As far as I know, this does not work from any of the mobile apps, though ...
As Andy mentioned, this option is already available. Todoist never deletes any of your completed tasks, you can always enter a project in which you've completed tasks, click on "Get completed tasks" at the bottom and simply un-check each completed task. They will stay there forever unless you click on the "Delete completed" link.
Alternatively, you could create a template for your project and easily import a group of tasks at once. Please check this video to see how it works: https://www.youtube.com/watch?v=_Rl_CLGY_3o