XR Toolkit , interacting with AR placed prefabs

with Unity's XR toolkit you can interact (translate, scale and rotate) with placed prefabs (on a plane) .
However, I can only get this to work if I use the ARPlacementInteractable.cs script to place object manually. Used teh Interaction example in the ARFoundations sample projects.
Does anybody know how i can use the XR interaction toolkit without the ARPlacementInteractable script. I would like to automatically place the prefab once a plane is detected.
thx, volker