Not sure I understand the question exactly. Generally, a file picker UI could look exactly the same in VR as it does out of VR, just projected on a flat surface

Not sure I understand the question exactly. Generally, a file picker UI could look exactly the same in VR as it does out of VR, just projected on a flat surface. The crucial point is to remain inside the stereoscopic VR view since exiting VR is very disruptive.