When editing your notes, you might need to select content that doesn't fully show on your page at a time. In this case, you can scroll while selecting your content. However, if this doesn't seem to work, make sure that you continue dragging your cursor even after the note frame finishes.
If you're scrolling down, dragging your cursor after the formatting tools will help you.
On the other hand, when you're scrolling up, you might need to drag your cursor all the way up to the title of your stream.