I get this question fairly often, and I always end up going to a very old work around, ie making a sketch in the view, to create the hinge line.
As you can see, there isn't a hinge line, that will project the view, to show the bend angle. Users often ask "why can't I jusst pick one of the bend lines, and have it project 'along' that ?"
So have I missed the boat? is there a better way to do this, besides creating a hinge sketch?
Maybe something like this?