Please bear with me if I'm using terms incorrectly...as my graphic arts (Viscom) program was a few years ago, and I'm somewhat rusty by now. I might mention that I think the app could be much more "user-friendly" (and much less productive of hair-pulling) and--in my case--seems to have been partly related to a poor (and very egotistical) instructor/head of the dept. (who used a lot of profanity and was insulting and abusive of his students) at this local college. Luckily, I could not locate my service revolver in those days. ; (
OK, a lot of the problems I had were related to projects like one where you take an object like a train engine, on one page, then--on an overlaying layer--draw its outline. This is a complex figure, and it was necessary to draw a number of pathways...which you DO NOT want closed. Like you might draw an ellipse like figure...but want to stop before you completely close it (and leave it right there). I guess what I'm trying to say is that I want to terminate the path, but NOT close it.
I constantly was confronted by AI wanting to close the path...or..when I moved to create another path, wanted to join two figures. I think I went around this by using a lot of layers, but this seemed an "ass-backwards" solution (and I soon accumulated LOTS of error messages). I'm also inclined to think that whoever invented "Bezier curves" should be drawn and quartered, and the creator of the "Pen Tool" should be shot (but these are separate issues). ; )