I've just started to play Limbo, and I wonder if there is a key combination to jump longer rather than the usual jump with a single key stroke.
There is no way to boost your jump distance in Limbo.
This is a deliberate feature made to increase the difficulty of the puzzles, by forcing the player to think of more strategic solutions than "just jump over it".
I've been playing the game for the last few days, and I've found out that there are two types of jumps:
There are some parts in the game where you have to use the Longer Jump. Otherwise, it becomes impossible to pass that level.
You can test the normal jump and the longer jump on a flat horizontal surface. I usually use the longer jump for convenience.