IgorB:

More I would suggest to insert the word "sequence" near "Sub project", because a professional user know so; and in Load window you find "Nest sequence" option. .
 
OK, I am going to rewrite what I wrote based on your original email.  We had no idea what "sequence" meant and thought it was Italian for something else (!).  Now I looked it up in reference to Video Editing and Final Cut Express uses it a lot so now I have a much better understanding.  I used Sub project because I thought it was more related to what Deim was talking about. 

On the manual, in "Camera and Projector" section, I think it would be important to add the two images that you find in "Cinelerra CV Manual.htm" and I add here. I know, they are drawn by hand but it is important to understand how camera and projector work.
 
I agree but I really do not like the hand drawing.