All scribble contents can be exported in Png format and saved under the
same directory folder Storage\Note\(same name as the source file).
Progress
It displays the chapter name (book name if no chapter), page progress,
last/next chapter, page number, slideshow, undo, and redo.
Tap on the page number to enter a quick-flip interface. Click the page
numbers again and input number to jump to the page directly.