Edit Done history. What is this?

“Edit Done history” is not “set a reminder”. This is for editing Done page.

E.g. If you just completed the task “Check blood pressure”. Now you can add extra note such as your blood pressure rate & diary on this page.

So you can record this additional note to DONE history page.

Later you can check when, what did you do & how was it.

Also if you want to edit completion date & time, you can do so as well.

If I want to set a reminder with this history, how can I do?

In that case, tap “Clone”. Then you can set a copy of new active reminder.

Can I add a note/diary without creating a reminder?

Yes. tap vertical 3 dots > Add a new Note/Diary. You can do from here.