In Xcode, there is a keyboard shortcut to hide the navigator, ⌘,0. But it stopped working. I went to system preferences and manually added it back a few days ago but it disappeared again today suddenly. Why does this keep happening?
I just realized that I had the developer documentation window open. For some reason, when this window is open, the "Hide Navigator" keyboard shortcut is no longer active. For all currently open Xcode windows. However, the command (⌘, 0) works only once to close the navigator in the developer documentation window then stops working until you close the window.