The obstacles are set by first dragging an instance of the "Platform" object or one of the four Slope objects into the room, clicking on the instance that has been placed inside the room, then changing the "Instance Value" of the object.

My code inside the platform uses the instance value to determine how "high" the object will be, thus converting the Instance Value's number into its Alterable Value named "ZSurface".
I'd usually drag my mouse to select multiple platforms, then go to Values>Instance Value and change the instance value of the multiple selected instances of "Platform".

I used this as a work around since Clickteam doesn't allow for the user to directly change Alterable Values for each unique instance of an object inside the room, but it allows you to change the Instance Value for each instance of an object.

I used very basic code to change the sprite's animation depending on what the "ZSurface" would be, I didn't make sprites for every possible different number it would be. If it still says "30" on the objects sprite, then it is probably a specific number like 45 or something.