not sure with 2d but i know with the third person character you can use the jump max hold time which limits how long the character can keep jumping. basically allowing the character to keep going up as long as jump is held, the option itself is what places a limit on how long the jump can last. in your particular case you could set it to about 1 second, then is the player holds jump for 1 second they will go to the height accordingly, but if they release before 1 second it will stop the jump when they release. guess a bit hard to explain but check it out. in the third person character if you click the class defaults near the top, then look in the details panel for the character section, in the character section you will find the jump max hold time option as well as the max jump count option.