Unity 5.6f3 - Enter/Leave VR button on top of VR lenses/distortion

Hey,

I cannot find a wait to draw a cardboard-style icon for leaving VR mode and entering "magic window" mode.

I wonder if i could really draw on top of the VR distortion/lenses, on the bottom left corner of the screen, where is it black.

Tried using render textures and cameras with different depth, but no success...

My app is a daydream/cardboard app, using native unity 5.6 VR.

Has anyone found a way to do that?

Thanks,