Not possible I'm afraid, at the moment 360 VR does not support legends.
It's the first time we hear this user request, but we can consider this for a future update:
- Do you expect the exact same legend as in SceneViewer, or are there differences to be considered?
- Would you want the legend to show always, or somehow be showable/hideable by a button? Or by some other logic? (Note this would need to work for both the immersive VR as well as the non-immersive desktop / phone experience.)