NavSim with Unity 3D - Help with Scenario Creation

Hello, I have been trying to run a custom scenario after following steps mentioned in the documentation.

Currently, we have demo_1.json and demo_2.json at ~/isaac/packages/navsim/scenarios and upon changing this code to a different obstacle and robot prefab (Cube and TrianlgeRobot respectively), it still spawns and simulates the default (Cylinder and Carter_Wheeled) in Unity.

Here is mydemo.json in the same directory

  "scene": "warehouse",
  "description": "Drive from garage door to back of warehouse, encounter an unexpected obstacle",
  "robots": [
      "prefab": "TriangleRobot",
      "name": "robot",
      "node": "navsim",
      "pose": [0.931374, 0, 0, 0.364064, 4.91, 0.85, 0.05]
  "frames": [
      "name": "pose_as_goal",
      "pose": [0.707107, 0, 0, 0.707107, -8.12, -6, 0]
  "obstacles": [
      "prefab": "Cube",
      "name": "obstacle in hallway",
      "pose": [1, 0, 0, 0, 0.13, -4.67, 1]

Here is the command I am using to run the simulation with the new JSON file:

~/isaac/packages/navsim/unity$ ./navsim.x86_64 --scene warehouse --scenario 0 --mydemo.json /home/robot/isaac/packages/navsim/scenarios

and here is the command I use to run the navigation app:

~/isaac$ bazel run //apps/carter/navsim:navsim_navigate -- --more packages/navsim/maps/warehouse.json,packages/navsim/robots/triangle_robot.json

I have 2 questions:

  1. What am I missing to make it work with the new configuration?
  2. Eventually, is it possible to spawn my own robot (urdf) into this simulation in place of the carter robot? or is it just the 4 given options (Carter_Wheeled, RectangleRobot, TriangleRobot, and CircleRobot) that I can play with

I would appreciate any advice/help
Thanks in advance!