I'm sorry for not answering your question, but it sounds like you are trying to build coasters around the paths? So you're trying to build a path to the entrance/exit to the coaster before actually placing the coaster itself? Why not buy the coaster and put it in the place you want it, then start a path (queue or exit path) beginning from the entrance or exit?
So instead of designing your coaster around your path, build your path around the coaster! Again, sorry for not answering your actual question and immediately offering an alternative, but this is how I do it when I play.
Ah, I understand what you mean now. Because of the complex coasters you get stuck trying to get "out of" the spiderweb of tracks. Yep, that can be hard. It also doesn't help that the game is a isometric top-down 2D pixel game. :D
As Die4Ever already said, your best bet is probably the bridge building mode and working your way out from the entrance, and rotate the view while you wiggle your way out.