ARKit image detection. Candidate image not listed

Hi, I try to use the new image detection feature in 4.20 preview 4. I’ve created an ARsession and a ARCandidateImage asset with a texture as image to detect. But I am not able to go further because the ARCandidateImage is not listed in the ARsession settings, I am not able to choose it as the target. Is there someting specific to do to get the the ARCandidateImage asset listed ? Is it broken or I do it wrong ?

Try preview 5, just released.