The Scene Builder as of EA is described that way in the documentation: Inspector covers the 5 up tabs of the side panel, and Layers panel stands below.
But this is not consistent with what we've in View menu:
View > Hide Inspector masks the whole side panel, Inspector + Layers as it should mask only the upper part and let Layers visible.

So either the doc is wrong and Inspector covers the whole side panel, Layers included.
Or the implementation is wrong and Hide Inspector should mask only the upper part.

I wonder if it wouldn't be clearer to have three terms:
- Inspector, the upper part made of the 5 tabs
- Layers, the bottom part made of a single panel (do we keep Layers as name here is a good question but another story, let not mix it here)
- Side Panel, the union of Inspector and Layers.

Then in View menu we should read Hide Side Panel where we read today Hide Inspector.