I see that other people have mentioned losing track of the layers panel, and people have rightly pointed out that it can be restored by View > Panels > Layers.
But in my install on MacOS 10.14.3, the layers panel has disappeared entirely from the list.
Same thing when I right click on the gray area above the browser. Layers panel doesn't exist.
Unless I'm missing something here – QGIS is * functionally unusable without the layers panel *. I tried
restarting qgis trashing the preferences restarting the machine reinstalling an earlier version (3.4) but no luck!