I have long paths and filenames showing in my helm session and I want to quickly look at one and then go back to the normal view. You can see my long paths and filenames below:
There are several related things that helm will do. One of them is
C-] Toggle Details, which gives toggles the view (starting with the above) shown below:
This only shows the full filenames though, and I also want to view the paths.
Another option in GUI emacs is to mouseover a result, but the path is so long that the hover text goes off the screen ('fml', nothing worse than thinking you've been saved by contextual hover menu/text, which then jumps off the screen anyway :D)
That last one is important, because what I want to do, ideally, is toggle truncation for a selection of lines (or just the current line) with a key command.