P3: Somewhat important Description
There is an example how to implement stereoscopic rendering for your presentation in qtquick3d\tests\manual\stereoscopic. Consider if there should also be a ready-made stereoscopic view?
Possible implementation options could be a) add stereoMode and eyeSeparation properties into QQuick3DViewport or b) implement QQuick3DStereoViewport inheriting QQuick3DViewport. This should have both C++ & QML APIs and settings be available in viewer app.
With this approach it would be easier to view any Quick3D presentation in stereoscopic. But rendering would be limited to common modes (top-down, left-right, anaglyph?) while current example approach allows implementing custom stereoscopic modes.