It is a bit tricky.
You can check out the "Monk Fight" template in the main page of Construct 3 and see an implementation of such a classic beat them up.
Keeping in mind there is a perspective and a shadow under the character, jump is actually a state you need to implement for your character.
It means your shadow represents the X and Y position of the feet of your character, where it is actually standing on the ground.
But visually you will move your character to be at a different position, and the feet will actually be away from the shadow.
This will give you the visualisation of a jump.
It also means that you will have to handle the collisions in a different way, because of the current position of the character.