I wonder how it is possible to anchor a child GameObject after the AR camera has detected an image target or model target (initial pose). Vuforia could then be turned off to prevent further tracking which often seems to be unstable. The HoloLens tracking takes over. I've found a link where somebody did that with an image target but the github project seems to miss some prefabs and uses lagacy versions of Vuforia and HoloToolKit.
I'm relatively new to Vuforia/Unity. Would be great to discuss this issue.