I'm looking for a chess GUI that shows the evaluation of each possible move rather than the top move.
In most GUIs you can set up top x moves. The reason why there is no program showing all moves, is that it would be terribly slow if you would make it show a lot of moves because of the engine.
All engines use some version of Alpha-Beta Search, without getting in the details of it, the point is, if a move is outside the interval of Alpha-Beta it is not examined further, so you can't really decide if it's right out of the window, or way off. If the engine wouldn't use this filtering, than it would need to check all branches, making it way too slow.
I don't think there is a GUI like that, if there is than the results it shows are completely bad, they would have the strength of a chess program from the 50s.