A room where nothing is written in code: the floor, the ledge and four crates are a JSON document, and so is the gravity. Each object says what it is made of with a physics2d component, and the scene says how hard things fall with a physics-world-2d on its root. This is what an editor saves.
The engine cannot move any of it. It keeps colliders, writes them down and reads them back without being able to simulate them, and the one line that changes that is installPhysics2d(). Take it out and the room still opens, still draws and still saves every collider: it just sits still. That is not a degraded mode, it is the mode a level editor runs in.
A collider carries no position. The object owns that, the same as its picture does, which is why moving an object in an editor moves what it collides with. And it is centred on that position, like a sprite.