Your customizations in AR mode keep their positions between sessions. It’s called “persistent anchor.” It’s available in both Quest 2 and 3.
But they can lose their positions sometimes. It can happen if you launch the AR mode after a very long time. It’s also lost when you clear cookies.
You can fix it using the “Move All” feature in the AR Space menu.
*This feature will be updated in XR Friend R and Pose Simulator soon.