It is possible without external addons. You'll have to set up all the events to handle Z elevation yourself (gravity, jump, block heights, and collision). There's literally a user working on a Landstalker remake here in the forums: construct.net/en/forum/construct-3/your-construct-creations-9/landstalker-remake-183858 & youtube.com/watch
Unfortunately, there's no easy way around it. As a reference on how to achieve this, you can look for the `3D Platformer` example, specifically in the "Update the entire 3D physics system for the player." block of the Gameplay event sheet. (`Avalanche` is another good example of how to handle the Z axis)
If you were to do this in a pure 2D game, you'd have to replace the Z (Z Elevation) with an Instance variable that tracks the height of each block. Probably in a Family of block objects.
Or, you could stick with Z Elevation and make a 3D game using `Ortographic projection` in such a way that it looks like a pure 2D game.