How do I reference a tilemap if it is in a different Collection to my script?

Questions
#1

I would like to create an RPG multi-screen game where each screen contains a dynamically generated tile map. I want to initialise all the tile maps at the start of the game.

I am trying to use the RPG game sample as a starting point. This contains a grid of 3x3 pre-defined tile maps, and as an experiment, I am trying to modify one of these tile maps by calling tilemap.set_tile("/1-1#tiles", "layer", x, 1, 0) in the game init(), where 1-1 refers to the tile map at the centre of the game grid. But I get an error:

ERROR:SCRIPT: main/game.script:14: Instance /1-1#tiles not found
stack traceback:
  [C]:-1: in function set_tile
  main/game.script:14: in function <main/game.script:3>

I cannot find the correct way to reference the tilemap. I obtained the URL from the right hand side info panel, but it does not work. However I notice that the game object 1-1 is part of a test_layout.collection, not the main.collection that game.script is in.

What is the correct way to reference this tilemap? Can anyone help please?

Screenshot 2023-04-16 192920
Screenshot 2023-04-16 1929201134×798 73.2 KB

#2

How is the test_layout.collection used? Is it added to another collection or is it loaded from a collection proxy?

The simplest way to figure out the URL if you are unsure is to add a .script file to the same game object as the tilemap and print(msg.url()) to see the full absolute URL to the gameobject.