Edit:
The path shown is not neccesarily the path the magnet takes:
Here (Lvl 7) it looks as if one could throw the magnet through the hole between the block and the ground. But the magnet gets blocked by the big block:
Just as a note, the last level is actually solvable by throwing the magnet through the box, that's actually how I solved it during my playthrough lol
This way is a lot easier:
