It depends how your enemy is set up initially. If I were to try to do a similar air combo effect in Construct I would give my enemies the "Platform" behavior. Then when you hit the enemy I would modify their Y vector parameter to move them in an upwards direction. Once they are in the air you could keep re-applying the Y vector movement every time they are hit in the air.
You could also modify their max fall speed to make it more floaty when they are being hit. Though be sure to reset the fall speed once the air combo is over and you want them to fall to the ground at normal speed. And you would probably want to vary the amount of Y vector motion depending on the size of the enemy.
It would take a lot of tweaking to get just right, unfortunately there is no quick and easy way to do air combo's buttery smooth like in Marvel vs Capcom. There could possibly be a plugin for it or something in the Scirra store you could buy, but I have never searched for one.