I thought it'd be nice to put down somewhere what this mod actually does on a technical level, just to avoid incompatibilities or other issues cropping up later. Note that this will go into some amount of code, and will contain fully unmarked spoilers for the game.

Using ModUtils, it first checks to see if the player is in Night's Bridge Station, at Platform B. Afterwards, it checks if the player is in a postgame state (by checking the "defeated Aleph Null" flag) and finally, it looks for the Amber Lodge prefab asset.

Once it's found all of the above, it teleports Amber a few coordinates to the left, unlocks the door on that instance of the object, and sets the destination of the object's WarpRegion to the Amber Café map, at which point custom mapping and object hierarchies take over and vanilla objects aren't modified. That's all!