Hide Android Emulator menu bar

You can use xdotool:

First you should find the id of that window

$ xdotool selectwindow  //After you use this line you should select the window
12345678

And you just minimize it.

$ xdotool windowminimize 12345678

xdotool is available as a package in at lease Debian, Ubuntu and Fedora.

And you can install this tool with this line.

$ sudo apt-get install xdotool

Credits: https://stackoverflow.com/a/26704369/3139930

On Windows you may try windows-specific hack via 3rd party tool.

• Take WinSpy (https://sourceforge.net/projects/winspyex/)
• Follow instructions on screenshot

I've found an alternative solution, you can move this sidebar by holding Alt key + click on the box. If you move the emulator, the sidebar will be placed on the default position.