I was working on a note file for 1 Peter 18-22 (tough one to translate and interpret - wow), and meant to scroll up on my notes. Instead, I hit the delete button and lost a note, and I had long forgotten where it came from.
Ctrl-Z and it was back!
I mention this, even though it may be obvious to some of you. There is no clear "undo" function in L4, so keep this in mind when you think you have lost something.
Jerry