When you maximise apps to fullscreen on Mac OS Sierra, the menu bar is hidden. This is expected, because it's full screen, but if you're using an app with tabs (like Visual Studio Code), the menu bar often drops down when you're trying to switch tabs. This can be infuriating.
Google Chrome doesn't have this issue because the developers have cleverly coded the app to move the tab bar down when the menu bar appears. Unfortunately this option isn't available in Firefox or Visual Studio Code.
I've been trying to find a way to permanently show the menu bar when apps are fullscreened as a workaround.