Even though no notepad exists from the kobo firmware, I thought of a way we can easily create a workaround
1 - What we first need to do is create a dummy epub book called, whatelse? Notepad with only a few key words like ... Grocerylist Notes Thoughts Ideas etc... whatever you want.
2 - Then just highlight the text and create a note under the selected word.
I know it's a few extra keystrokes than a simple notepad app in the beta features but I think it should work
albeit a little clunky it should partially satisfy the notepad need.
We could place a sample epub book here for people to use.