Vertical 3-way/lane movement?

Hi there!

I have a code for my characters movement, which currently looks like this:

     void FixedUpdate () {
         //0 i Y vil sige at vi ikke kan bevæge os i Y-aksen, altså ikke hoppe!
         input = new Vector3 (Input.GetAxisRaw("Horizontal"), 0, Input.GetAxisRaw("Vertical"));
                 
         if(rigidbody.velocity.magnitude < maxSpeed)
         {
             rigidbody.AddForce(input * moveSpeed);
         }
         
         //Dø hvis Players transform y er lavere end -2 (altså hvis han falder udover banens kant)
         if (transform.position.y < -2)
         {
             Die();
         }
         
         
         Physics.gravity = Physics.Raycast(transform.position, Vector3.down, .55f) ? Vector3.zero : new Vector3(0,-60f,0);
         
         
     }

He's moving fine and dandy, but I was wondering if there's a way to make the player move a certain amount in the vertical direction, when pressing Up and Down?

I wish to make 3 lines/paths in the z-axis the player can jump "in and out" of, then run along on the x-axis as usual.

Here's a picture of what I mean:

Any help is appreciated!

Thanks.