Hi gus_massa,
Thank you for sharing your feedback.
When you press share button only the current state of the app is shared.
Since this application, does not track your data or session.
So that's why this feature is not working as you expected because it is not designed for it.
You can create tasks and share it as to-do list.
Currently when you press "Finish", is it not possible to undo, I will try to include in next release.
Again thank you for taking time to add your feedback, I really value that and appreciate it.
Take Care, Have a nice day