It’s still on our todo list to support this directly, but I wanted to mention that it’s currently possible to password protect a note in a roundabout way: by importing a password protected PDF into the note. This will password protect the note with the password of the PDF. You can even delete the PDF from the note and the password will remain on the note.
You can add a shortcut to your Home Screen to open a specific notebook (see http://feedback.squidnotes.com/knowledgebase/articles/1179331) or to create a new note in a specific notebook (see http://feedback.squidnotes.com/knowledgebase/articles/1179328).
It does not appear to be possible to create a widget that allows for taking handwritten notes directly on the Home Screen (due to the fact that you need to be able to swipe left/right to get to different pages on your Home Screen). Please vote here if you’re interested in a widget that shows a particular note on your Home Screen (and allows you to open it quickly to edit it).